best practices for windows server 2000-2003 disk partitioning and volume design

8/6/2019 Best Practices for Windows Server 2000-2003 Disk Partitioning and Volume Design

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Best Practices forWindows Server 2000/2003

Disk Partitioning and Volume Design

By: Craig BorysowichChief Technology Architect

Imagination Edge Inc.

www.imedge.net


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IntroductionThis whitepaper addresses the need for a stable design of disk and volume layouts to ensure that a server is

robust and highly available. This paper discusses a series of industry Best Practices and advice on

designing a solution for proper installation that provides redundancy and fault tolerance, but maintains the

highest levels of performance.

Drive Types

There are wide ranges of drive types available, but the lion share of server hardware available leverages the

SCSI standard for providing local disk solutions. However, SATA, Ultra ATA, iSCSI, or SAN/NAS

solutions are also compatible. The one thing to keep in mind is that off-board disk will likely not perform

as well as on-board dedicated disk to the server. So it is recommended to have at least two local hard

drives for OS, logs etc. and then connect via iSCSI, Ethernet, or Fiber Channel to a SAN/NAS solution.

The higher the speed of the drives the better for performance as well. Taking 15000RPM drives over

10000 RPM drives is recommended for performance.

Software vs Hardware RAID

RAID stands for Redundant Array of Inexpensive Disk and provides a methodology for combining large

numbers of disks into single contiguous partitions and/or providing heightened levels of data redundancy

within a disk partition. There are two possible ways to implement RAID: Hardware RAID and Software

RAID.

Hardware RAID

The hardware-based system manages the RAID subsystem independently from the host and presents to the

host only a single disk per RAID array.

An example of a Hardware RAID device would be one that connects to a SCSI controller and presents the

RAID arrays as a single SCSI drive. An external RAID system moves all RAID handling "intelligence"

into a controller located in the external disk subsystem. The whole subsystem is connected to the host via a

normal SCSI controller and appears to the host as a single disk.RAID controllers also come in the form of cards that act like a SCSI controller to the operating system but

handle all of the actual drive communications themselves. In these cases, you plug the drives into the RAID

controller just like you would a SCSI controller, but then you add them to the RAID controller's

configuration, and the operating system never knows the difference.

Software RAID

Software RAID implements the various RAID levels in the OS disk (block device) code. It offers the

cheapest possible solution, as expensive disk controller cards or hot-swap chassis are not required.

Software RAID also works with cheaper IDE and ATA disks as well as SCSI disks.

For optimum performance, it is recommended to go with the hardware RAID solution. As more volumes

are created and more advanced levels of RAID are implemented, the software-based RAID can consume a

lot of CPU and memory. The hardware RAID controller should also have a battery backed write Cache toensure that sudden power outages do not lose any data.

Note: Before you can use the software RAID in Windows Server 2003, you must convert basic disks to

dynamic disks. In addition, dynamic disks are not supported on cluster storage.

Raid Levels

There are various different levels or methods that can be used to implement RAID technology


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Factors RAID-0 RAID-1 RAID-5 RAID-0+1

Minimum number

of disks

2 2 3 4

Usable storage

capacity

100 percent 50 percent (N-1)/N disks,

where N is the

number of disks

50 percent

Fault tolerance None. Losing asingle disk causes

all data on the

volume to be lost.

Can lose multipledisks as long as a

mirrored pair is not

lost.

Can tolerate theloss of one disk.. Can lose multipledisks as long as a

mirrored pair is not

lost

Read performance Generally

improved by

increasing

concurrency.

Up to twice as

good as JBOD

(assuming twice

the number of

disks).

Generally

improved by

increasing

concurrency.

Improved by

increasing

concurrency and

by having multiple

sources for each

request.

Write performance Generally

improved by

increasing

concurrency.

Between 20

percent and 40

percent worse than

JBOD for most

workloads.

Worse unless

using full-stripe

writes (large

requests).

Can be as low as

25 percent of

JBOD. Can be

worse or better

depending on

request size.

Best use Temporarydata only

Operatingsystem

Log files

User andshared data1

Applicationfiles

2

Operatingsystem

User andshared data

Applicationfiles

Log Files

For operating system purposes, RAID 1 is perfect. With the minimum size of drives available increasing to

36GB, it is unlikely that you would need to use RAID 0+1 for your system/boot partition. Use only RAID

1 where possible. With the popularity of blade and 1U servers that only allow for two drives, this RAID 1

configuration will become a standard very quickly. The rest of the disk in a system can be used for data in

a RAID 5 configuration.

Basic vs. Dynamic Disk

Windows Server 2000/2003 allows for the configuration of both Basic and Dynamic Disk. Where possible

in a Windows Server 2000/2003 implementation, you should configure all of your partitions as dynamic so

that they can grow when space becomes limited. The performance of a partition seriously degrades when

the free space is below 20%, so dynamic disk can help solve this issues by increasing the space available.

Basic Disks

In essence, a basic disk contains basic volumes, such as primary partitions, extended partitions, and logicaldrives. When you use basic disks, you're limited to creating four primary partitions per disk or three

primary partitions and one extended partition with unlimited logical drives. Although these limitations are

real, they aren't as severe as you might think. Basic and dynamic disks differ in the number of partitions (on

basic disks) and volumes (on dynamic disks) that each can contain. Basic disks also use the partition tables

stored in the Master Boot RecordMBRat the beginning of the disk. To make matters even more

confusing, basic disk volumes also include support for multi-disk volumessuch as volume sets, stripe

sets, mirror sets, and stripe sets with parity.


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As a Win2K and NT 4.0 administrator, you've used basic disks and probably have had occasion to "get

fancy" by using volume sets, mirror sets, or stripe sets. However, you might have noticed some limitations

with basic disks, such as having to reboot the system after you make changes to the disk configuration.

Dynamic Disks

The limitations of basic disks and other inconveniences drove the creation of a new type of disk definitionfor Windows systemsthe dynamic disk. When you initialize a physical disk as dynamic, it's called a

dynamic disk and contains dynamic volumes, such as simple volumes, spanned volumes, striped volumes,

mirrored volumes, and RAID 5 volumes. Dynamic disk storage is divided into volumes instead of

partitions. Dynamic storage lets you manage disks and volumes without restarting Windows.

On a basic disk, a partition is a portion of the disk that functions as a physically separate unit. A physical

disk unit can contain any combination of storage types. However, all volumes on the same disk must use

the same storage type. A volume is a storage unit derived from free space on one or more dynamic disks.

You can format both partitions and volumes with a file system and assign a drive letter. Volumes also have

different layouts (e.g., simple volumes, spanned volumes, striped volumes) and characteristics. Basic disks

used to provide different layout types (e.g., spanned, mirrored, RAID 5) with partitions. However, dynamic

disks provide these layouts in dynamic disk volumes. Other dynamic disk limitations include lack of

support for removable storage devices (i.e., IEEE 1394 FireWire- and USB-attached disks) and an irritation

when using Windows Cluster Service.Dynamic disks introduce the concept of disk groups. Disk groups (collections of disks organized as

entities) help administrators prevent data loss by organizing dynamic disks. All dynamic disks within a disk

group store configuration data for the entire group (this data is stored in a 1MB region at the end of each

dynamic disk). All configuration information for simple, spanned, mirrored, striped, or RAID 5 volumes

within a disk group are stored on each disk in the group. This "database" of configuration information is

replicated and kept up-to-date across all dynamic disks in the group. If you lose a dynamic disk or you

move the disk group to another system, the OS maintains the configuration information for the disk group.

Win2K systems allow only one disk group (Disk Group 0DG0) per computer. Microsoft will probably

extend this disk-group functionality in future Windows releases.

Volumes and partitions on the system/boot disk should be configured as dynamic wherever possible.

Partition and volume layout

The RAID 1 pair that you have created can now be broken in to a series of volumes for use by the

Operating System and it's various components.

When performing a base install of the OS from CD, you will be prompted to create the Boot/Install

partition on the hard drive. It is considered to be a best practice to set this partition at 10GB. This means

entering a value of 10,240 MB when entering the partition size.

Once the server has completed installation, you can create more partitions on the volume and organize the

content of the OS accordingly. Depending on the size of the drives you are using, you may want to create

one or two more partitions. Be sure to convert the install partition to be dynamic disk instead of basic disk.

This will allow you to grow the partition later if needed. You should plan to leave 20-40% of the total

volume space unpartitioned


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Sample Volume Layout

Using an example of two 36GB HDDs configured as a RAID 1 mirrored pair and leaving 36GB of space to

be assigned, here is a sample of layout of how the disk should be broken into volumes.

Partition Size Purpose

1 10GB EFI Boot partition and Windows Server 2000/2003 system disk2 2-16GB Page File Partition - should be set to double the size of the page file

required.

3 2GB Active Log Files Volume

Free Space 8GB 20% Available for dynamic allocation to the other three volumes in

case the get full

It is important to separate all logs from the system/boot partition. In case of a serious blue screen condition

or corruption on the system volume that requires a rebuild or restore of that partition, you will still have a

preserved set of logs on the other volume. These can then be used for forensic purposes to aid in problem

determination from the previous build. If you want to simplify the configuration in the table above, then

you can merge partition 2&3 together and store your active logs with the extended page file. All other

applications and data should be installed on a separate RAID5 disk array or SAN/NAS volume. After

installing applications, you may want to grow the log space and keep all server and application logs on thesame volume so that they are easier to find or can be collected by log aggregation servers more easily.

Page File configuration

You should change the configuration of your paging files to reduce the space requirement on partition 1

To change the size of the virtual memory paging file

1. Open System in Control Panel.2. On the Advanced tab, under Performance, clickSettings.3. In the Performance Options dialog box, click the Advanced tab.4. Under Virtual memory, clickChange.5. Under Drive [Volume Label], click the drive that contains the paging file you want to change.

6. Under Paging file size for selected drive, clickCustom size, and type a new paging file size inmegabytes in the Initial size (MB) or Maximum size (MB) box, and then clickSet.

If you decrease the size of either the initial or maximum page file settings, you must restart your

computer to see the effects of those changes. Increases typically do not require a restart.

A best practice is to set the page file total size to 1.5 times the amount of RAM on the server. So a server

with 4GB of RAM should have a 6GB page file. Page files will also grow dynamically as needed, so you

should set the partition to double the size of the page file or in this example 12GB.

Blue screen memory dumps typically land on the c: drive or system partition. It is considered a best

practice to make the page file on the system partition the minimum size allowed by the OS - usually the

exact memory size - then set the maximum size to be equal to the minimum. Add a page file to cover the

rest of the page file size requirements on the second partition (likely drive D). This will guarantee space is

available for the memory dumps during a STOP condition and allow the page file to run amok on a separatepartition. Running multiple page files this way may also enhance server performance. So, the minimum

size of the second page file should be set to 50% of the ram size with the maximum being set to the exact

memory size.

Microsoft recommends that you create a paging file for each physical volume on the system. On most

systems, multiple paging files can improve the performance of virtual memory. Thus, instead of a single

large paging file, it's better to have many small ones. Keep in mind that removable drives don't need paging

files.


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Moving Log Files

Best Practice is to move the logs off of the system/boot partition to ensure that the files are available in case

of a blue screen or a volume corruption that requires the system partition to be reformatted. Keeping a

drive location where all logs from the OS and other applications can be collected make it easier to

troubleshoot and also provides a single point for log aggregation tools to collect their information.

By default, Event Viewer log files use the .evt extension and are located in the following folder:

%SystemRoot%\System32\Config

To move Event Viewer log files to another location on the hard disk, follow these steps:

1. ClickStart, and then clickRun.2. In the Open box, type regedit, and then clickOK.

3. Locate and click the following registry key:HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Eventlog

4. Click the subkey that represents the event log that you want to move, for example, clickApplication.

5. In the right pane, double-clickFile.6. Type the complete path to the new location (including the log file name) in the Value data box,

and then clickOK.

For example, if you want to move the application log (Appevent.evt) to the Eventlogs folder on

the E drive, type e:\eventlogs\appevent.evt.

7. Repeat steps 4 through 6 for each log file that you want to move.8. ClickExit on the Registry menu.9. Restart the computer.

best practices for windows server 2000-2003 disk partitioning and volume design

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