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Hitachi Command Suite

Dynamic Link Manager(for Solaris) User Guide

MK-92DLM114-40

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iiHitachi Dynamic Link Manager (for Solaris) User Guide

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Contents

Preface.................................................................................................xiiiIntended audience...................................................................................................xivProduct version....................................................................................................... xivRelease notes..........................................................................................................xivDocument organization............................................................................................ xivRelated documents...................................................................................................xvDocument conventions............................................................................................. xvConventions for storage capacity values.................................................................... xviAccessing product documentation............................................................................ xviiGetting help........................................................................................................... xviiComments..............................................................................................................xvii

1 Overview of HDLM................................................................................1-1What is HDLM?.......................................................................................................1-2HDLM features........................................................................................................1-2

2 HDLM functions.................................................................................... 2-1Devices managed by HDLM..................................................................................... 2-3System configuration.............................................................................................. 2-3LU configuration..................................................................................................... 2-5Program configuration.............................................................................................2-6Position of the HDLM driver and HDLM device...........................................................2-8Logical device files for HDLM devices........................................................................2-9Distributing a load using load balancing..................................................................2-10

Paths to which load balancing is applied........................................................... 2-12When using the Hitachi AMS/WMS series................................................ 2-12When using other than the Hitachi AMS/WMS series................................ 2-13When using a global-active device.......................................................... 2-14

Load balancing algorithms...............................................................................2-14Performing failovers and failbacks using path switching........................................... 2-16

Automatic path switching................................................................................ 2-16Automatic failovers................................................................................2-17Automatic failbacks................................................................................2-18

Manual path switching.....................................................................................2-19Path status transition...................................................................................... 2-20

iiiHitachi Dynamic Link Manager (for Solaris) User Guide

The online path status........................................................................... 2-20The offline path status...........................................................................2-21Status transitions of a path.................................................................... 2-21

Intermittent error monitoring (functionality when automatic failback is used)............ 2-24Checking intermittent errors............................................................................ 2-24Setting up intermittent error monitoring........................................................... 2-24Intermittent error monitoring actions............................................................... 2-25

When an intermittent error occurs.......................................................... 2-25When an intermittent error does not occur..............................................2-26When the conditions for an intermittent error are changed during errormonitoring............................................................................................ 2-27When failures occur on all paths while monitoring for intermittent errors...2-27

When a user changes the intermittent error information.................................... 2-28Detecting errors by using path health checking....................................................... 2-29Distributing a load by using the dynamic I/O path control function........................... 2-30

What is the dynamic load balance control function............................................ 2-30Dynamic I/O path control function................................................................... 2-31

Error management................................................................................................2-31Types of collected logs....................................................................................2-32Filtering of error information............................................................................2-34Collecting error information using the utility for collecting HDLM error information(DLMgetras)................................................................................................... 2-35

Collecting audit log data........................................................................................ 2-35Categories and audit events that HDLM can output to the audit log....................2-37Requirements for outputting audit log data.......................................................2-40Destination and filtering of audit log data......................................................... 2-41Audit log data formats.....................................................................................2-42

Integrated HDLM management using Global Link Manager.......................................2-44Cluster support..................................................................................................... 2-45

3 Creating an HDLM environment............................................................. 3-1HDLM system requirements.....................................................................................3-3

Hosts and OSs supported by HDLM....................................................................3-3Storage systems supported by HDLM................................................................. 3-4

Storage systems......................................................................................3-4HBAs......................................................................................................3-6When handling intermediate volumes managed by Hitachi RapidXchange....3-6

Cluster software supported by HDLM................................................................. 3-6Volume manager supported by HDLM................................................................ 3-7Combinations of cluster software and volume managers supported by HDLM........3-7

For the Solaris Cluster or VCS environment............................................... 3-7When creating an Oracle RAC 11g environment.........................................3-9When creating an Oracle RAC 12c environment....................................... 3-17

Virtualization environments supported by HDLM................................................3-20Memory and disk capacity requirements........................................................... 3-22

Memory requirements............................................................................3-22Disk capacity requirements.................................................................... 3-22

Number of LUs and paths supported in HDLM...................................................3-23Flow for creating an HDLM environment................................................................. 3-24HDLM installation types......................................................................................... 3-24Notes on creating an HDLM environment................................................................ 3-25

Notes on hardware settings............................................................................. 3-25

ivHitachi Dynamic Link Manager (for Solaris) User Guide

Notes on installation....................................................................................... 3-26Notes on related software............................................................................... 3-30Notes on command execution..........................................................................3-31Notes on the disk label....................................................................................3-31Notes on linking with Global Link Manager........................................................3-31

Installing HDLM.................................................................................................... 3-31Preparations for a new installation of HDLM......................................................3-31

Performing operations on devices to be managed by HDLM......................3-31Apply Solaris patches.............................................................................3-33Set up the hardware..............................................................................3-33Set up the /kernel/drv/sd.conf file.......................................................... 3-34Set up the /etc/system file..................................................................... 3-34Set up the /etc/syslog.conf or /etc/rsyslog.conf file..................................3-35Set up VxVM......................................................................................... 3-35Set up SVM...........................................................................................3-36Set up Solaris Cluster.............................................................................3-36Setting up a Solaris 11 environment........................................................3-38

Preparation for performing an unattended installation of HDLM..........................3-39Performing a new installation of HDLM............................................................. 3-40Performing a new installation of HDLM (when Solaris Cluster is being used)........3-47Using the HDLM device unconfiguration function when performing a new installationof HDLM.........................................................................................................3-57Preparations for an upgrade installation or re-installation of HDLM..................... 3-58Performing an upgrade installation or re-installation of HDLM............................ 3-58Installing HDLM in an LDoms environment........................................................3-63

Configuring a boot disk environment...................................................................... 3-67Overview of configuring a boot disk environment.............................................. 3-68Procedure for configuring a boot disk environment............................................3-68

Migration from an existing HDLM environment.........................................3-69Migration by installing HDLM in the existing local boot disk environment... 3-70Migration by installing HDLM in the existing boot disk environment........... 3-72Migration by building a new pre-migration environment........................... 3-74Setting up the post-migration environment..............................................3-76

Configuring a boot disk environment for a ZFS file system....................................... 3-81Boot disk environment that uses a ZFS file system............................................ 3-81Creating a ZFS boot disk environment (for Solaris 10)....................................... 3-83

Preparing for creating a boot disk environment........................................3-83Copying the local boot disk environment to the LUs (HDLM device) in thestorage system......................................................................................3-83

Creating a ZFS boot disk environment (for Solaris 11)....................................... 3-86Preparing for creating a boot disk environment........................................3-86Moving a local boot disk environment to an LU (HDLM device) in a storagesystem..................................................................................................3-86Configuring a ZFS boot disk environment after the migration....................3-87Performing a check after restart............................................................. 3-89

Migrating from a ZFS boot disk environment to the local boot disk environment (forSolaris 10)......................................................................................................3-90Migrating from a ZFS boot disk environment to the local boot disk environment (forSolaris 11)......................................................................................................3-92

Creating a new boot environment...........................................................3-92Configuring the post-migration ZFS boot disk environment....................... 3-94Migrating to the ZFS boot disk environment............................................ 3-95

vHitachi Dynamic Link Manager (for Solaris) User Guide

Performing a check after restart............................................................. 3-96Migrating from an environment where a physical device is specified, to anenvironment where a logical device is specified.................................................3-96

Migrating from a boot disk environment to the local boot disk environment...............3-98Configuring a mirrored boot disk environment incorporating SVM........................... 3-103

Precautions.................................................................................................. 3-103Configuring a boot disk environment in which HDLM manages the boot disk andmirroring the environment by using SVM........................................................ 3-104

Configuring a boot disk environment in which HDLM manages the boot disk,from the local boot disk environment.................................................... 3-104Mirroring a boot disk environment in which HDLM manages the boot disk byusing SVM...........................................................................................3-105

Placing the boot disks under HDLM management by installing HDLM to a mirroredboot disk environment incorporating SVM....................................................... 3-108

Installing HDLM and then configuring the environment...........................3-109Placing the boot disks under HDLM management...................................3-109

Removing HDLM........................................................................................... 3-115Excluding the prepared LUs from HDLM management............................ 3-115Configuring an environment and then removing HDLM........................... 3-115

Checking the path configuration........................................................................... 3-120Setting up HDLM functions...................................................................................3-121

Checking the current settings.........................................................................3-121Setting up the HDLM functions.......................................................................3-122

Setting up load balancing..................................................................... 3-123Setting up path health checking............................................................3-123Setting up the automatic failback function............................................. 3-124Setting up intermittent error monitoring................................................ 3-124Setting up dynamic I/O path control..................................................... 3-125Setting the error log collection level...................................................... 3-125Setting the trace level.......................................................................... 3-126Setting the error log file size.................................................................3-127Setting the number of error log files......................................................3-127Setting the trace file size......................................................................3-128Setting the number of trace files...........................................................3-128Setting up audit log data collection....................................................... 3-128Setting the audit log facility..................................................................3-129

Checking the updated settings....................................................................... 3-130Setting up integrated traces.................................................................................3-131

Notes on using the Hitachi Network Objectplaza Trace Library..........................3-132Displaying the Hitachi Network Objectplaza Trace Library setup menu.............. 3-132Changing the size of integrated trace files.......................................................3-133Changing the number of integrated trace files.................................................3-133Changing the buffer size per monitoring interval duration................................ 3-134Adjusting the number of messages to be output per monitoring interval........... 3-135Finishing the Hitachi Network Objectplaza Trace Library settings...................... 3-136Applying the Hitachi Network Objectplaza Trace Library settings...................... 3-136

Creating file systems for HDLM (when volume management software is not used)...3-137Setting up VxVM................................................................................................. 3-138

Creating a disk group.................................................................................... 3-139Creating VxVM volumes.................................................................................3-141Removing devices from VxVM........................................................................ 3-142

Devices to be removed from VxVM........................................................3-142

viHitachi Dynamic Link Manager (for Solaris) User Guide

Removing devices from VxVM on a controller basis................................ 3-144Removing devices from VxVM on a path basis........................................3-148Actions to be taken if an sd or ssd device has not been suppressed from VxVM..........................................................................................................3-152

Introducing VxVM while using HDLM.............................................................. 3-156Linking VxVM and Solaris Cluster....................................................................3-156

Setting up SVM................................................................................................... 3-158Notes...........................................................................................................3-158Registering HDLM devices..............................................................................3-159

To use a local volume.......................................................................... 3-159To use a shared diskset....................................................................... 3-160

Setting up VCS....................................................................................................3-162Configuring systems that use verified boot............................................................3-163

SPARC systems that support the verified boot function of Oracle ILOM............. 3-163For legacy SPARC systems.............................................................................3-163

Removing HDLM................................................................................................. 3-164Overview of HDLM removal............................................................................3-164Preparations for HDLM removal......................................................................3-164

Performing operations on HDLM-managed devices.................................3-164Remove Solaris Cluster settings............................................................ 3-166Remove VCS settings........................................................................... 3-168Remove VxVM settings.........................................................................3-168Remove SVM settings.......................................................................... 3-169

Removing HDLM........................................................................................... 3-170Removing HDLM from the local boot disk environment........................... 3-170Removing HDLM from the boot disk environment...................................3-172Removing HDLM from an LDoms environment....................................... 3-172

Settings needed after HDLM removal..............................................................3-177VxVM settings..................................................................................... 3-177SVM settings....................................................................................... 3-177Solaris Cluster settings.........................................................................3-177File system settings............................................................................. 3-178Application program settings................................................................ 3-179Verified boot settings........................................................................... 3-179

Removing Hitachi Network Objectplaza Trace Library (HNTRLib2).....................3-180Removing Hitachi Network Objectplaza Trace Library (HNTRLib)...................... 3-180

4 HDLM operation....................................................................................4-1Notes on using HDLM..............................................................................................4-2

Displaying path information...............................................................................4-2When a path error is detected........................................................................... 4-2iostat command................................................................................................4-2Storage system................................................................................................ 4-3Command execution......................................................................................... 4-3Using a sun HBA...............................................................................................4-3Starting Solaris in single-user mode................................................................... 4-3Upgrading Solaris............................................................................................. 4-4Operation in single-user mode...........................................................................4-4

Initializing HDLM when the host is started in single-user mode................... 4-4Tasks that can be performed in single-user mode......................................4-5

Maintenance tasks on devices connected by paths in the boot disk environment... 4-6HDLM operations using commands...........................................................................4-6

viiHitachi Dynamic Link Manager (for Solaris) User Guide

Notes on using commands................................................................................ 4-6Viewing path information.................................................................................. 4-6Changing the status of paths.............................................................................4-7

Changing the status of paths to Online..................................................... 4-7Changing the status of paths to Offline(C).................................................4-8

Viewing LU information..................................................................................... 4-9Displaying corresponding information about an HDLM device, sd or ssd device, andLDEV............................................................................................................... 4-9Initializing statistical information for paths........................................................ 4-10Viewing and setting up the operating environment............................................4-11

Viewing the operating environment.........................................................4-11Setting up the operating environment.....................................................4-11

Viewing license information............................................................................. 4-12Updating the license....................................................................................... 4-13Viewing HDLM version information...................................................................4-13Viewing HDLM component information............................................................. 4-14

Starting and stopping the HDLM manager...............................................................4-15Starting the HDLM manager............................................................................ 4-15Stopping the HDLM manager........................................................................... 4-15

HDLM resident processes.......................................................................................4-16Changing the configuration of the HDLM operating environment.............................. 4-16

Precautions regarding changes to the configuration of an HDLM operatingenvironment...................................................................................................4-17

Changing the configuration of a system that uses HDLM.......................... 4-17When the path configuration is changed................................................. 4-18When the path configuration is changed in a boot disk environment......... 4-19

Overview of reconfiguring the HDLM device......................................................4-20Reconfiguring the HDLM device.............................................................. 4-20Notes on reconfiguring the HDLM device.................................................4-21

Adding a new logical unit................................................................................ 4-22Notes................................................................................................... 4-22Adding a new LU (when not using Solaris Cluster)................................... 4-23Adding a new LU by restarting the nodes (when using Solaris Cluster)...... 4-25Adding a new LU via dynamic reconfiguration (when using Solaris Cluster)4-31

Configuration changes such as deleting a logical unit........................................ 4-36Changing the configuration by restarting the host....................................4-37Deleting an LU via dynamic reconfiguration............................................. 4-42

Adding a path to an existing LU by dynamic reconfiguration...............................4-44Deleting a path to an existing LU by dynamic reconfiguration.............................4-47Specifying whether a logical unit is to be managed by HDLM (when not using SolarisCluster)..........................................................................................................4-49

Changing an HDLM-managed device to a non-HDLM-managed device.......4-49Changing a non-HDLM-managed device to an HDLM-managed device.......4-50

Specifying whether a logical unit is to be managed by HDLM (when using SolarisCluster)..........................................................................................................4-52

Changing an HDLM-managed device to a non-HDLM-managed device.......4-52Changing a non-HDLM-managed device to an HDLM-managed device (whenthe node must be restarted)...................................................................4-57Changing a non-HDLM-managed device to an HDLM-managed device (fordynamic reconfiguration)....................................................................... 4-63

Inheriting logical device names during storage system migration........................4-67

viiiHitachi Dynamic Link Manager (for Solaris) User Guide

5 Troubleshooting....................................................................................5-1Information collected by using the DLMgetras utility for collecting HDLM errorinformation.............................................................................................................5-2Checking error information in messages................................................................... 5-2What to do for a path error..................................................................................... 5-3

Examining the messages...................................................................................5-5Obtain path information.................................................................................... 5-5Identifying the error path..................................................................................5-5Narrowing down the hardware that might have caused the error......................... 5-5Identifying the error location and correcting any hardware errors.........................5-5Placing the path online......................................................................................5-5

Actions to take for a path error in a boot disk environment........................................ 5-6Path errors during boot processing.................................................................... 5-6

When a path error occurs at the initial stage of boot processing................. 5-6When a path error occurs after the HDLM driver starts path processing.......5-6

Path errors after boot processing completes....................................................... 5-7What to do for a program error................................................................................5-7

Examining the messages...................................................................................5-8Obtaining program information..........................................................................5-8What to do for the program error...................................................................... 5-8Contacting your HDLM vendor or maintenance company..................................... 5-9

What to do for other errors......................................................................................5-9

6 Command reference..............................................................................6-1Overview of the HDLM command dlnkmgr................................................................ 6-2clear (returns the path statistics to the initial value).................................................. 6-3

Format.............................................................................................................6-3To set the path statistics to 0...................................................................6-3To display the format of the clear operation.............................................. 6-3

Parameters...................................................................................................... 6-3To set the path statistics to 0...................................................................6-3To display the format of the clear operation.............................................. 6-4

help (displays the operation format).........................................................................6-4Format.............................................................................................................6-4Parameter........................................................................................................6-4

offline (places paths offline).....................................................................................6-6Format.............................................................................................................6-7

To place paths offline.............................................................................. 6-7To display the format of the offline operation............................................6-7

Parameters...................................................................................................... 6-7To place paths offline.............................................................................. 6-7To display the format of the offline operation.......................................... 6-11

online (places paths online)................................................................................... 6-12Format...........................................................................................................6-12

To place paths online.............................................................................6-12To display the format of the online operation.......................................... 6-12

Parameters.....................................................................................................6-12To place paths online.............................................................................6-12To display the format of the online operation.......................................... 6-16

set (sets up the operating environment)................................................................. 6-18Format...........................................................................................................6-18

To set up the HDLM operating environment............................................ 6-18

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To display the format of the set operation...............................................6-18Parameters.....................................................................................................6-18

To set up the HDLM operating environment............................................ 6-18To display the format of the set operation...............................................6-33

view (displays information).................................................................................... 6-34Format...........................................................................................................6-34

To display program information..............................................................6-34To display path information....................................................................6-35To display LU information...................................................................... 6-35To display HBA port information............................................................. 6-36To display CHA port information............................................................. 6-36To display corresponding information about an HDLM device, sd or ssd device,and LDEV..............................................................................................6-36To display the format of the view operation.............................................6-36

Parameters.....................................................................................................6-36To display program information..............................................................6-37To display path information....................................................................6-44To display LU information...................................................................... 6-57To display HBA port information............................................................. 6-69To display CHA port information............................................................. 6-71To display corresponding information about an HDLM device, sd or ssd device,and LDEV..............................................................................................6-72To display view operation format............................................................6-73

monitor (displays I/O information at a specified interval)......................................... 6-74Format...........................................................................................................6-75

To display I/O information for each HBA port.......................................... 6-75To display I/O information for each CHA port.......................................... 6-75To display the monitor operation format................................................. 6-75

Parameters.....................................................................................................6-75To display I/O information for each HBA port.......................................... 6-76To display I/O information for each CHA port.......................................... 6-77To display monitor operation format....................................................... 6-78

add (adds a path dynamically)............................................................................... 6-79Format...........................................................................................................6-79

To add a path dynamically..................................................................... 6-79To display the format of the add operation..............................................6-79

Parameters.....................................................................................................6-79To add a path dynamically..................................................................... 6-79To display the format of the add operation..............................................6-80

delete (deletes a path dynamically)........................................................................ 6-80Format...........................................................................................................6-81

To delete a path dynamically..................................................................6-81To display the format of the delete operation.......................................... 6-81

Parameters.....................................................................................................6-81To delete a path dynamically..................................................................6-81To display the format of the delete operation.......................................... 6-82

refresh (applies storage system settings to HDLM).................................................. 6-82Format...........................................................................................................6-82

To apply storage system settings to HDLM.............................................. 6-82To apply the latest model ID to HDLM.................................................... 6-82To display the format of the refresh operation.........................................6-82

Parameters.....................................................................................................6-82

xHitachi Dynamic Link Manager (for Solaris) User Guide

To apply storage system settings to HDLM.............................................. 6-82To apply the latest model ID to HDLM.................................................... 6-84To display the format of the refresh operation.........................................6-84

7 Utility reference....................................................................................7-1Overview of the utilities...........................................................................................7-3The DLMgetras utility for collecting HDLM error information.......................................7-4

Format.............................................................................................................7-5Parameters...................................................................................................... 7-5List of collected error information...................................................................... 7-7

The dlmcfgmgr utility for managing the HDLM configuration.................................... 7-18Format...........................................................................................................7-19Parameters.....................................................................................................7-19

The dlminstcomp HDLM component installation utility..............................................7-21Format...........................................................................................................7-21Parameter...................................................................................................... 7-21

The dlmsetboot utility for assisting configuration of an HDLM boot disk environment. 7-21Format...........................................................................................................7-22Parameters.....................................................................................................7-22

The dlmsetconf utility for creating the HDLM driver configuration definition file......... 7-22Format...........................................................................................................7-23Parameters.....................................................................................................7-23Items in the storage-system-migration definition file......................................... 7-28

The dlmsetdevname utility for setting an HDLM logical device name ........................ 7-29Format...........................................................................................................7-29Parameters.....................................................................................................7-29

The dlmstart utility for configuring HDLM devices.................................................... 7-29Format...........................................................................................................7-29Parameters.....................................................................................................7-29Note.............................................................................................................. 7-30

The dlmvxexclude utility for assisting creation of the VxVM configuration file.............7-31Format...........................................................................................................7-31Parameters.....................................................................................................7-31

The dlmzfsboot utility for assisting configuration of an HDLM ZFS boot disk environment........................................................................................................................... 7-33

Format...........................................................................................................7-33Parameters.....................................................................................................7-33Log file...........................................................................................................7-34

The installhdlm utility for installing HDLM................................................................7-34Format...........................................................................................................7-35Parameters.....................................................................................................7-35Contents of the installation-information settings file.......................................... 7-35About the log file............................................................................................ 7-43Note.............................................................................................................. 7-44

installux.sh utility for HDLM common installer......................................................... 7-45Format...........................................................................................................7-45Parameters.....................................................................................................7-45Log file...........................................................................................................7-46Note.............................................................................................................. 7-46

The removehdlm utility for removing HDLM............................................................ 7-47Format...........................................................................................................7-47Parameters.....................................................................................................7-47

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The dlmpresanboot utility for processing before a boot disk is configured................. 7-47Format...........................................................................................................7-47Parameters.....................................................................................................7-48

The dlmpostsanboot utility for processing after a boot disk is configured...................7-48Format...........................................................................................................7-48Parameters.....................................................................................................7-48

8 Messages............................................................................................. 8-1Before viewing the list of messages..........................................................................8-3

Format and meaning of message IDs.................................................................8-3Terms used in messages and message explanations........................................... 8-3Components that output messages to syslog...................................................... 8-3

KAPL01001 to KAPL02000....................................................................................... 8-4KAPL03001 to KAPL04000......................................................................................8-31KAPL04001 to KAPL05000......................................................................................8-33KAPL05001 to KAPL06000......................................................................................8-41KAPL06001 to KAPL07000......................................................................................8-50KAPL07001 to KAPL08000......................................................................................8-52KAPL08001 to KAPL09000......................................................................................8-53KAPL09001 to KAPL10000......................................................................................8-57KAPL10001 to KAPL11000......................................................................................8-84KAPL11001 to KAPL12000....................................................................................8-129KAPL13001 to KAPL14000....................................................................................8-132KAPL15001 to KAPL16000....................................................................................8-140Return codes for Hitachi Command Suite Common Agent Component..................... 8-144

A Functional differences between versions of HDLM...................................A-1Functional differences between version 6.1 or later and versions earlier than 6.1........ A-2Functional differences between version 6.0 or later and versions earlier than 6.0........ A-2Precautions on differences in functionality between HDLM 5.6.1 or earlier and HDLM5.6.2 or later..........................................................................................................A-2

Acronyms and abbreviations

Glossary

Index

xiiHitachi Dynamic Link Manager (for Solaris) User Guide

Preface

This document describes how to use the Hitachi Dynamic Link Manager.

□ Intended audience

□ Product version

□ Release notes

□ Document organization

□ Related documents

□ Document conventions

□ Conventions for storage capacity values

□ Accessing product documentation

□ Getting help

□ Comments

Preface xiiiHitachi Dynamic Link Manager (for Solaris) User Guide

Intended audienceThis document is intended for storage administrators who use HitachiDynamic Link Manager (HDLM) to operate and manage storage systems, andassumes that readers have:

• Knowledge of Solaris and its management functionality• Knowledge of Storage system management functionality• Knowledge of Cluster software functionality• Knowledge of Volume management software functionality

Product versionThis document revision applies to HDLM for Solaris v8.5.1 or later.

Release notesRead the release notes before installing and using this product. They maycontain requirements or restrictions that are not fully described in thisdocument or updates or corrections to this document. Release notes areavailable on Hitachi Data Systems Support Connect: https://knowledge.hds.com/Documents.

Document organizationThe following table provides an overview of the contents and organization ofthis document. Click the chapter title in the left column to go to that chapter.The first page of each chapter provides links to the sections in that chapter.

Chapter/Appendix Description

Chapter 1, Overview of HDLMon page 1-1

Gives an overview of HDLM, and describes its features.

Chapter 2, HDLM functions onpage 2-1

Describes management targets and the systemconfiguration of HDLM, and the basic terms andfunctions for HDLM.

Chapter 3, Creating an HDLMenvironment on page 3-1

Describes the procedures for setting up an HDLMenvironment and the procedure for canceling thosesettings.

Chapter 4, HDLM operation onpage 4-1

Describes how to use HDLM by using both the HDLMGUI and commands, and how to manually start andstop the HDLM manager. This chapter also describeshow to configure an environment to properly operateHDLM, such as changing the HDLM management-target devices that connect paths or replacing thehardware that makes up a path. describes how tocheck path information by using the Windowsmanagement tool.

xiv PrefaceHitachi Dynamic Link Manager (for Solaris) User Guide

https://knowledge.hds.com/Documentshttps://knowledge.hds.com/Documents

Chapter/Appendix Description

Chapter 5, Troubleshooting onpage 5-1

Explains how to troubleshoot a path error, HDLMfailure, or any other problems that you mightencounter.

Chapter 6, Command referenceon page 6-1

Describes all the HDLM commands.

Chapter 7, Utility reference onpage 7-1

Describes the HDLM utilities.

Chapter 8, Messages on page8-1

Provides information about viewing messages outputby HDLM. It also lists and explains the HDLM messagesand shows the actions to be taken in response to eachmessage.

Appendix A, Functionaldifferences between versions ofHDLM on page A-1

Gives precautions on differences in functionalitybetween HDLM versions.

Related documentsThe following related Hitachi Command Suite documents are available on thedocumentation CD:

• Hitachi Command Suite Global Link Manager User Guide, MK-92HC214• Hitachi Command Suite Global Link Manager Installation and

Configuration Guide, MK-95HC107• Hitachi Command Suite Global Link Manager Messages, MK-95HC108• File Access Library & File Conversion Utility for Solaris HP-UX AIX

Windows Tru64 UNIX NCR SVR4 DYNIX/ptx Linux

Document conventionsThis document uses the following typographic conventions:

Convention Description

Bold • Indicates text in a window, including window titles, menus, menuoptions, buttons, fields, and labels. Example:Click OK.

• Indicates a emphasized words in list items.

Italic • Indicates a document title or emphasized words in text.• Indicates a variable, which is a placeholder for actual text

provided by the user or for output by the system. Example:pairdisplay -g group(For exceptions to this convention for variables, see the entry forangle brackets.)

Preface xvHitachi Dynamic Link Manager (for Solaris) User Guide

Convention Description

Monospace Indicates text that is displayed on screen or entered by the user.Example:pairdisplay -g oradb

< > angledbrackets

Indicates a variable in the following scenarios:• Variables are not clearly separated from the surrounding text or

from other variables. Example:Status-.csv

• Variables in headings.

[ ] squarebrackets

Indicates optional values. Example: [ a | b ] indicates that you canchoose a, b, or nothing.

{ } braces Indicates required or expected values. Example: { a | b } indicatesthat you must choose either a or b.

| vertical bar Indicates that you have a choice between two or more options orarguments. Examples:[ a | b ] indicates that you can choose a, b, or nothing.{ a | b } indicates that you must choose either a or b.

underline Indicates the default value.Example:

[ a | b ]

Conventions for storage capacity valuesPhysical storage capacity values (for example, disk drive capacity) arecalculated based on the following values:

Physical capacity unit Value

1 kilobyte (KB) 1,000 (103) bytes

1 megabyte (MB) 1,000 KB or 1,0002 bytes

1 gigabyte (GB) 1,000 MB or 1,0003 bytes

1 terabyte (TB) 1,000 GB or 1,0004 bytes

1 petabyte (PB) 1,000 TB or 1,0005 bytes

1 exabyte (EB) 1,000 PB or 1,0006 bytes

Logical capacity values (for example, logical device capacity, cache memorycapacity) are calculated based on the following values:

Logical capacity unit Value

1 block 512 bytes

1 cylinder Mainframe: 870 KBOpen-systems:

xvi PrefaceHitachi Dynamic Link Manager (for Solaris) User Guide

Logical capacity unit Value

• OPEN-V: 960 KB• Others: 720 KB

1 KB 1,024 (210) bytes

1 MB 1,024 KB or 1,0242 bytes

1 GB 1,024 MB or 1,0243 bytes

1 TB 1,024 GB or 1,0244 bytes

1 PB 1,024 TB or 1,0245 bytes

1 EB 1,024 PB or 1,0246 bytes

Accessing product documentationProduct documentation is available on Hitachi Data Systems SupportConnect: https://knowledge.hds.com/Documents. Check this site for themost current documentation, including important updates that may havebeen made after the release of the product.

Getting helpHitachi Data Systems Support Connect is the destination for technical supportof products and solutions sold by Hitachi Data Systems. To contact technicalsupport, log on to Hitachi Data Systems Support Connect for contactinformation: https://support.hds.com/en_us/contact-us.html.

Hitachi Data Systems Community is a global online community for HDScustomers, partners, independent software vendors, employees, andprospects. It is the destination to get answers, discover insights, and makeconnections. Join the conversation today! Go to community.hds.com,register, and complete your profile.

CommentsPlease send us your comments on this document: [email protected] the document title and number, including the revision level (forexample, -07), and refer to specific sections and paragraphs wheneverpossible. All comments become the property of Hitachi Data SystemsCorporation.

Thank you!

Preface xviiHitachi Dynamic Link Manager (for Solaris) User Guide

https://knowledge.hds.com/Documentshttps://support.hds.com/en_us/contact-us.htmlhttps://community.hds.com/welcomemailto:[email protected]

xviii PrefaceHitachi Dynamic Link Manager (for Solaris) User Guide

1Overview of HDLM

HDLM is a software package that manages paths between a host and astorage system. HDLM is designed to distribute loads across multiple pathsand will switch a given load to another path if there is a failure in the paththat is currently being used, thus improving system reliability.

This chapter gives an overview of HDLM and describes its features.

□ What is HDLM?

□ HDLM features

Overview of HDLM 1-1Hitachi Dynamic Link Manager (for Solaris) User Guide

What is HDLM?With the widespread use of data warehousing and increasing use ofmultimedia data, the need for high-speed processing of large volumes of dataon networks has rapidly grown. To satisfy this need, networks dedicated tothe transfer of data, such as SANs, are now being used to provide access tostorage systems.

HDLM manages the access paths to these storage systems. HDLM providesthe ability to distribute loads across multiple paths and switch to another pathif there is a failure in the path that is currently being used, thus improvingsystem availability and reliability.

The figure below shows the connections between hosts and storage systems.A server on which HDLM is installed is called a host.

Figure 1-1 Connections between hosts and storage systems

For details about the storage systems supported by HDLM, see Storagesystems supported by HDLM on page 3-4.

HDLM featuresHDLM features include the following:

The ability to distribute a load across multiple paths. This is also known asload balancing.

When a host is connected to a storage system via multiple paths, HDLMcan distribute the load across all the paths. This prevents one, loadeddown path from affecting the processing speed of the entire system.For details on load balancing, see Distributing a load using load balancingon page 2-10.

1-2 Overview of HDLMHitachi Dynamic Link Manager (for Solaris) User Guide

The ability to continue running operations between a host and storagesystem, even if there is a failure. This is also known as performing a failover.

When a host is connected to a storage system via multiple paths, HDLMcan automatically switch to another path if there is some sort of failure inthe path that is currently being used. This allows operations to continuebetween a host and a storage system.For details on performing failovers, see Performing failovers and failbacksusing path switching on page 2-16.

The ability to bring a path that has recovered from an error back online. Thisis also known as performing a failback.

If a path is recovered from an error, HDLM can bring that path backonline. This enables the maximum possible number of paths to always beavailable and online, which in turn enables HDLM to better distribute theload across multiple paths.Failbacks can be performed manually or automatically. In automaticfailback, HDLM automatically restores the route to the active state afterthe user has corrected hardware problems in the route.For details on performing failbacks, see Performing failovers and failbacksusing path switching on page 2-16.

The ability to automatically check the status of any given path at regularintervals. This is also known as path health checking.

HDLM can easily detect errors by checking the statuses of paths at user-defined time intervals. This allows you to check for any existing patherrors and to resolve them promptly and efficiently.For details on setting up and performing path health checking, seeDetecting errors by using path health checking on page 2-29.

Overview of HDLM 1-3Hitachi Dynamic Link Manager (for Solaris) User Guide

1-4 Overview of HDLMHitachi Dynamic Link Manager (for Solaris) User Guide

2HDLM functions

This chapter describes the various functions that are built into HDLM. Beforethe function specifications are explained though, this chapter will go intodetail about the HDLM management targets, system configuration, and basicterms that are necessary to know to effectively operate HDLM. After that, therest of the chapter focus on describing all the HDLM functions, including themain ones: load distribution across paths and path switching.

□ Devices managed by HDLM

□ System configuration

□ LU configuration

□ Program configuration

□ Position of the HDLM driver and HDLM device

□ Logical device files for HDLM devices

□ Distributing a load using load balancing

□ Performing failovers and failbacks using path switching

□ Intermittent error monitoring (functionality when automatic failback isused)

□ Detecting errors by using path health checking

□ Distributing a load by using the dynamic I/O path control function

□ Error management

HDLM functions 2-1Hitachi Dynamic Link Manager (for Solaris) User Guide

□ Collecting audit log data

□ Integrated HDLM management using Global Link Manager

□ Cluster support

2-2 HDLM functionsHitachi Dynamic Link Manager (for Solaris) User Guide

Devices managed by HDLMBelow is a list of devices that can or cannot be managed by HDLM. Thedevices that can be managed by HDLM are called HDLM management-targetdevices.

HDLM management-target devices:The following devices are from the storage systems listed in Section Whatis HDLM? on page 1-2:

¢ SCSI devices (sd or ssd devices)¢ Boot disks#

¢ Swap devices#

¢ Dump devices#

#:If you want to use these disks as HDLM management-target devicesin the Solaris version 11.0 or earlier, assign VTOC labels to them. EFIlabels are not supported.

Non-HDLM management-target devices:

¢ SCSI devices (sd or ssd devices) other than those of the storagesystems listed in Section What is HDLM? on page 1-2

¢ Built-in disks in a host¢ Devices other than disks (tape devices, etc.)¢ Command devices of the storage systems listed in Section What is

HDLM? on page 1-2 (For example, Hitachi RAID Manager commanddevices.)

System configurationHDLM manages routes between a host and a storage system by using theSCSI driver (sd or ssd driver). The host and storage systems are connectedusing SAN with fiber cables or SCSI cables. The cable port on the host is ahost bus adapter (HBA). The cable port on the storage system is a port (P) ona channel adapter (CHA).

A logical unit (LU) contained in a storage system is the target of input to, oroutput from, the host. You can divide an LU into multiple areas. Each areaafter the division is called a Dev. The Dev is equivalent to a slice or partition.A route that connects a host and an LU is called a physical path, and a routethat connects a host and a Dev is called a path. When an LU has been dividedinto multiple Devs, the number of paths set to the LU is equal to the numberthat is found by multiplying the number of physical paths by the number ofDevs in the LU.

HDLM assigns an ID to each physical path and manages paths on a physical-path basis. Because you do not need to be aware of the difference betweenphysical paths and paths to operate HDLM, the following descriptions mightsimply refer to paths, without distinguishing between physical paths and


paths. The ID that HDLM assigns to each path (physical path) is called aAutoPATH_ID. A path is also sometimes called a managed object.

The following figure shows the HDLM system configuration.

Figure 2-1 HDLM system configuration

The following table lists and describes the HDLM system components.

Table 2-1 HDLM system components

Components Description

HBA A host bus adapter. This serves as a cable port on the host.

SAN A dedicated network that is used for data transfer between thehost and storage systems

CHA A channel adapter

P A port on a CHA. This serves as a cable port on a storagesystem.

LU A logical unit (a logical volume defined on the storage system).This serves as the target of input or output operations from thehost.

Dev An area (slice or partition) that is created when an LU is divided

Physical path A route that connects a host and an LU

Path A route that connects a host and a Dev


LU configurationAfter you have properly installed HDLM, the LU configuration will change asfollows:

Before the installation of HDLM:The host recognizes that an sd or ssd device is connected to each physicalpath.Thus, a single LU in the storage system is recognized as the samenumber of LUs as that of physical paths.

After the installation of HDLM:An HDLM device that corresponds one-to-one with the Dev in an LU in thestorage system is created above an sd or ssd device.Thus, from the host, LUs in the storage system are also recognized as oneLU regardless the number of physical paths.

After the installation of HDLM, an LU recognized by a host is called a host LU(HLU). The areas in a host LU that correspond to the Devs (slice or partition)in a storage system LU are called host devices (HDev).

On a system using HDLM, the logical device file for the HDLM device is usedto access the target LU instead of the logical device file for the sd or ssddevice.

The logical device files for sd or ssd are deleted by HDLM.

The following figure shows the LU configuration recognized by the host, afterthe installation of HDLM.


Figure 2-2 LU configuration recognized by the host after the installation ofHDLM

The following table lists and describes the components recognized by thehost.

Table 2-2 Components recognized by the host

Components Description

HLU An LU that the host recognizes via the HDLM driver. It iscalled a host LU. No matter how many physical pathsexist, one host LU is recognized for one LU in the storagesystem.

HDev A Dev (a slice or partition) in an LU that the hostrecognizes via the HDLM driver. It is called a host device.No matter how many physical paths exist, one hostdevice is recognized for one Dev in the storage system.

Program configurationHDLM is actually a combination of several programs. Because each programcorresponds to a specific HDLM operation, it is important to understand thename and purpose of each program, along with how they are all interrelated.

The following figure shows the configuration of the HDLM programs.


Figure 2-3 Configuration of the HDLM programs

The following table lists and describes the functions of these programs.

Table 2-3 Function of HDLM programs

Program name Functions

HDLM command Provides the dlnkmgr command, which enables you to:• Manage paths• Display error information• Set up the HDLM operating environment

HDLM utility Provides the HDLM utility, which enables you to:• Collect error information• Add a new LU and delete an existing LU

(reconfiguring an HDLM device dynamically)• Create an HDLM driver configuration definition file (/

kernel/drv/dlmfdrv.conf)• Create a correspondence table of logical device files

when migrating to HDLM 6.5.1• Support the creation of a VxVM configuration file• The unattended installation of HDLM• Install Hitachi Command Suite Common Agent

Component

HDLM manager Provides the HDLM manager, which enables you to:• Configure the HDLM operating environment


Program name Functions

• Request path health checks and automatic failbacksto be performed

• Collect error log data

HDLM alert driver Reports the log information collected by the HDLM driverto the HDLM manager. The driver name is dlmadrv.

HDLM driver Controls all the HDLM functions, manages paths, anddetects errors. The HDLM driver consists of the following:• Core logic component

Controls the basic functionality of HDLM.• Filter component

Sends and receives I/O data. The driver name isdlmfdrv.

• HDLM nexus driverPerforms operations such as reserving controllernumbers for logical device files of the HDLM device,and managing HDLM driver instances for each HBAport. The driver name is dlmndrv.

Position of the HDLM driver and HDLM deviceThe HDLM driver is positioned above the SCSI driver. Each application on thehost uses the HDLM device (logical device file) created by HDLM, to accessLUs in the storage system. The following figure shows the positions of theHDLM driver and HDLM devices.


Figure 2-4 Position of the HDLM driver and HDLM devices

Logical device files for HDLM devicesWhen you install HDLM, a logical device file to be used by HDLM will becreated for each LU on a per-Dev (slice) basis. Setting this logical device filename in an application, such as volume management software, enables theapplication to access an LU by using the HDLM function.

The logical device files existing before HDLM installation (the logical devicefiles of an sd or ssd) will be deleted.

The following explains the names and locations of the logical device files forHDLM devices

Logical device file names for HDLM devicesThe logical device file name of an HDLM device is a changed version ofthe controller number of the logical device file name of the sd or ssddevice. For example, let us assume that an LU has two physical paths,


and for one of the Dev (slices) in that LU, the corresponding logical devicefile names of the sd or ssd devices are c2t1d1s0 and c3t2d1s0. In thiscase, when you install HDLM, these logical device files will be deleted.Then, a logical device file that has a different controller number, such asc4t1d1s0, is created for the HDLM device.The following explains each part of the logical device file name formatcUtXdYsZ:U

The controller number reserved by HDLM using a nexus driver

XThe target ID or WWN (World Wide Name) of the sd or ssd device thatcorresponds to the HDLM device

YThe LUN of the sd or ssd device that corresponds to the HDLM device

ZThe device slice number of the sd or ssd device that corresponds tothe HDLM device

NoteIf EFI labels are set for LUs, the HDLM logical device name, whichrepresents the entire LU, will be in the cUtXdY format.

Locations of logical device files for HDLM devicesBlock logical device files for HDLM devices are created in /dev/dsk.Character logical device files for HDLM devices are created in /dev/rdsk.

Distributing a load using load balancingWhen the system contains multiple paths to a single LU, HDLM can distributethe load across the paths by using multiple paths to transfer the I/O data.This function is called load balancing, and it prevents a single, heavily loadedpath from affecting the performance of the entire system.

Note that some I/O operations managed by HDLM can be distributed to eachpath, while others cannot. Therefore, even though load balancing function isused, I/O operations might not be equally allocated to each path.

Figure 2-5 Flow of I/O data when the load balancing function is not used onpage 2-11 shows the flow of I/O data when the load balancing function isnot used. Figure 2-6 Flow of I/O data when the load balancing function isused on page 2-12 shows the flow of I/O data when the load balancingfunction is used. Both figures show an example of an I/O being issued for thesame LU from multiple applications.


Figure 2-5 Flow of I/O data when the load balancing function is not used

When the load balancing function is not used, I/O operations converge onto asingle path (A). The load on that one physical path (A) will cause abottleneck, which might cause problems with system performance.


Figure 2-6 Flow of I/O data when the load balancing function is used

When the load balancing function is used, I/O operations are distributed viamultiple physical paths (A, B, C, and D). This helps to prevent problems withsystem performance and helps prevent bottlenecks from occurring.

Paths to which load balancing is appliedThis section describes, for each type of storage system, the paths to whichthe load balancing function is applied.

When using the Hitachi AMS/WMS series

When HDLM performs load balancing, it differentiates between load balancingamong owner paths and among non-owner paths. An owner path is a paththat passes through the owner controller for a target LU. This path is set onthe owner controller of the storage system LU. Because the owner controllervaries depending on the LU, the owner path also varies depending on the LU.A non-owner path is a path that uses a CHA other than the owner controller(a non-owner controller). The paths to be used are selected, in the order ofowner paths and non-owner paths. To prevent performance in the entiresystem from deteriorating, HDLM does not perform load balancing betweenowner paths and non-owner paths. When some owner paths cannot be useddue to a problem such as a failure, load balancing is performed among the


remaining usable owner paths. When all owner paths cannot be used, loadbalancing is performed among the non-owner paths.

For the example in Figure 2-7 Overview of load balancing on page 2-13,suppose that in the owner controller of LU0 is CHA0. When the LU isaccessed, the load is balanced between the two physical paths A and B, whichare both owner paths. When one of the paths (A) cannot be used, then theLU is accessed from the only other owner physical path (B). When both of theowner physical paths (A and B) cannot be used, the load is then balancedbetween two other, non-owner physical paths (C and D).

Figure 2-7 Overview of load balancing

When using other than the Hitachi AMS/WMS series

All online paths are owner paths. Therefore, for the example in Figure 2-6Flow of I/O data when the load balancing function is used on page 2-12, theload is balanced among the four physical paths A, B, C, and D. If one of thephysical paths were to become unusable, the load would be balanced amongthe three, remaining physical paths.

NoteLoad balancing is performed for the following storage systems:

¢ Universal Storage Platform V/VM series¢ Virtual Storage Platform series¢ Virtual Storage Platform G1000 series (VSP G1000 series)¢ Virtual Storage Platform G1500 (VSP G1500)¢ Virtual Storage Platform F1500 (VSP F1500)


¢ Virtual Storage Platform G200, G400, G600, G800 (VSP Gx00 models)¢ Virtual Storage Platform F400, F600, F800 (VSP Fx00 models)¢ Hitachi AMS2000 series#

¢ Hitachi SMS series#

¢ HUS100 series#

¢ HUS VM#: This storage system applies when the dynamic I/O path controlfunction is disabled.

When using a global-active device

The default settings of the storage system specify that all paths are ownerpaths. Load balancing is performed on all paths that access the primary andsecondary volumes of global-active device pairs.

However, if the primary site and the secondary site are far apart, I/Operformance might be low for I/O issued to a site other than the location ofthe host. In such a case, specify the non-preferred path option on the storagesystem at the site where the host is not located. A path for which the non-preferred path option is specified is a non-owner path and cannot be useduntil all the owner paths become unavailable.

If you specify the non-preferred path option on the storage system when theHDLM device is already configured, execute the refresh operation of theHDLM command, or execute the dlmsetconf utility for creating the HDLMdriver configuration definition file, and then restart the host.

Load balancing algorithmsHDLM has the following six load balancing algorithms:

• The Round Robin algorithm• The Extended Round Robin algorithm• The Least I/Os algorithm• The Extended Least I/Os algorithm• The Least Blocks algorithm• The Extended Least Blocks algorithm

The above algorithms are divided into two categories, which differ in theirprocessing method. The following describes both of these processingmethods:

The Round Robin, Least I/Os, and Least Blocks algorithmsThese algorithms select which path to use every time an I/O is issued.The path that is used is determined by the following:

¢ Round RobinThe paths are simply selected in order from among all the connectedpaths.


¢ Least I/OsThe path that has the least number of I/Os being processed isselected from among all the connected paths.

¢ Least BlocksThe path that has the least number of I/O blocks being processed isselected from among all the connected paths.

The Extended Round Robin, Extended Least I/Os, and Extended Least Blocksalgorithms

These algorithms determine which path to allocate based on whether theI/O to be issued is sequential with the immediately preceding I/O.If the I/O is sequential with the previous I/O, the path to which theprevious I/O was distributed will be used. However, if a specified numberof I/Os has been issued to a path, processing switches to the next path.If the I/O is not sequential with the previous I/O, these algorithms selectthe path to be used each time an I/O request is issued.

¢ Extended Round RobinThe paths are simply selected in order from among all the connectedpaths.

¢ Extended Least I/OsThe path that has the least number of I/Os being processed isselected from among all the connected paths.

¢ Extended Least BlocksThe path that has the least number of I/O blocks being processed isselected from among all the connected paths.

The following table lists and describes the features of the load balancingalgorithms.

Table 2-4 Features of the load balancing algorithms

Algorithm type Algorithm features

• Round Robin#

• Least I/Os• Least Blocks

These types of algorithms are most effective when a lot ofdiscontinuous, non-sequential I/Os are issued.

• Extended RoundRobin

• Extended Least I/Os• Extended Least

Blocks

If the I/O data is from something like a read request and isgenerally sequential with the previous I/Os, an improvementin reading speed can be expected due to the storage systemcache functionality. These types of algorithms are mosteffective when a lot of continuous, sequential I/Os are issued.

#Some I/O operations managed by HDLM can be distributed across all,available paths, and some cannot. Thus, you should be aware that even ifyou specify the Round Robin algorithm, some of the I/O operations willnever be issued uniformly across all the given paths.


The default algorithm is the Extended Least I/Os algorithm, which is set whenHDLM is first installed. When an upgrade installation of HDLM is performed,the algorithm that is currently being used is inherited.

Select the load balancing algorithm most suitable for the data access patternsof your system environment. However, if there are no recognizable dataaccess patterns, we recommend using the default algorithm, the ExtendedLeast I/Os algorithm.

You can specify the load balancing function by the dlnkmgr command's setoperation. For details on the set operation, see set (sets up the operatingenvironment) on page 6-18.

Performing failovers and failbacks using path switchingWhen the system contains multiple paths to an LU and an error occurs on thepath that is currently being used, HDLM can switch to another functionalpath, so that the system can continue operating. This is called a failover.

If a path in which an error has occurred recovers from the error, HDLM canthen switch back to that path. This is called a failback.

Two types of failovers and failbacks are available:

• Automatic failovers and failbacks• Manual failovers and failbacks

Failovers and failbacks switch which path is being used and also change thestatuses of the paths. A path status is either online or offline. An online statusmeans that the path can receive I/Os. On the other hand, an offline statusmeans that the path cannot receive I/Os. A path will go into the offline statusfor the following reasons:

• An error occurred on the path.• A user executed the HDLM command's offline operation.

For details on the offline operation, see offline (places paths offline) onpage 6-6.

For details on path statuses and the transitions of those statuses, see Pathstatus transition on page 2-20.

NotesSwitching a reserved path might take several seconds. A reserved path isswitched in the following cases:

¢ The reserved path is placed offline.¢ An owner path is placed online when a path has been reserved while

only non-owner paths are online.

Automatic path switchingThis section describes the automatic failover and automatic failback functionsthat automatically switch paths.


Automatic failovers

If you detect an error in a path being used, you can keep operating thesystem by changing the path state to offline, and using other online paths.This function is called automatic failover. Automatic failovers can be used forthe following levels of errors:

CriticalA fatal error that might stop the system.

ErrorA high-risk error, which can be avoided by performing a failover or someother countermeasure.

For details on error levels, see Filtering of error information on page 2-34.

When the Hitachi AMS/WMS series is being used, HDLM will select the path tobe used next from among the various paths that access the same LU, startingwith owner paths, and then non-owner paths. For example, in Figure 2-8 Pathswitching on page 2-18, the owner controller of LU is CHA0, and access tothe LU is made only via the physical path (A). After the access path is placedoffline, the first candidate for the switching destination is the physical path(B) and the second candidate is the physical path (C or D).

When the Universal Storage Platform V/VM series, Virtual Storage Platformseries, VSP G1000 series, VSP G1500, VSP F1500, VSP Gx00 models, VSPFx00 models, Hitachi AMS2000 series#, Hitachi SMS series#, HUS100 series#,or HUS VM is being used, all the paths are owner paths. This means that allthe paths that are accessing the same LU are possible switching destinations.For example, in Figure 2-8 Path switching on page 2-18, the LU is accessedusing only the one physical path (A). However, after that path is placedoffline, the switching destination can come from any of the other threephysical paths (B, C, or D).

#This storage system applies when the dynamic I/O path control function isdisabled.

Paths are switched in units of physical paths. Therefore, if an error occurs in apath, HDLM switches all the other paths that run through the same physicalpath.
