ht509076 how to add drives to a raid array

How to add hard disk drives to an existing RAID array (Virtual Drive, VD)With ServeRAID Mxxxx or ThinkSystem RAID controller

Machine Types: Any Lenovo ThinkSystem and IBM / Lenovo System x Server

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Contents

ContentsAuthors................................................................................ii

Contributors......................................................................... iiChapter 1 Introduction..........................................................1Chapter 2 Important Considerations before expanding a VD.....2

Changing Cache Policy during VD migration.........................3Before migration.............................................................3During migration.............................................................3After migration has completed........................................4

Chapter 3 Measurement examples..........................................5Influences on the expansion time.........................................5System x3650 M4.................................................................5Lenovo SR550......................................................................6A final word to the results.....................................................8

Chapter 4 Using StorCLI........................................................9Preparations before migration............................................10

Showing all RAID controllers installed..........................10Displaying more information for a specific RAID controller......................................................................11Changing a drive to Ugood............................................15

Adding drive(s) to a VD.......................................................16Preparing for migration.................................................16Initiating the migration..................................................16Checking migration progress........................................18Task to complete after migration finished.....................19

Chapter 5 ThinkSystem servers migration methods...............20Reconfiguring LXPM to boot into uEFI text mode................20Reconfiguring uEFI text mode to boot into LXPM................24uEFI text interface..............................................................28

Changing drive status...................................................29Expanding a VD.............................................................34

Lenovo XClarity Provisioning Manager...............................42Changing drive status...................................................43

Changing drives individually from JBOD to Unconfigured Good......................................45Changing more than one drive from JBOD to Unconfigured Good......................................49

Expanding a VD.............................................................52Chapter 6 Extending the file system......................................60

Windows Server..................................................................60Expanding the file system.............................................61

Chapter 7 Situations where the expansion of a VD will fail......64Two more common reasons for VD expansion to fail..........64

RAID volume is not using the full capacity of all drives. 64RAID Virtual Drive created with drives of different capacity........................................................................65

Displays when a RAID volume can not be expanded...........66StorCLI..........................................................................66Lenovo XClarity Provisioning Manager, LXPM...............67Text uEFI.......................................................................68

Only possible solution........................................................69Appendix A Sources............................................................70

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Authors

AuthorsChristian Flatscher Lenovo PFE for RAID products, Lenovo UK

Contributors

Han Tsai Advisory Product Engineer for ThinkSystem servers, Lenovo Taiwan

Guillermo Regulez Lenovo PE for RAID products, Lenovo Morrisville USA

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Chapter 1 Introduction

Chapter 1 IntroductionThis document explains the methods available on Lenovo System x and Lenovo ThinkSystem servers to expand a Virtual Drive, that is a RAID volume, by adding one or more (hard) disk drives to the server and adding these to an existing Virtual Drive – in short VD.

This document contains a lot of screen shots and detailed step-by-step instructions.

For easier understanding images have been cropped where possible.

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Chapter 2 Important Considerations before expanding a VD


Attention! Before expanding a VD it is important that the data on the VD that is to be expanded is backed up!

Before expanding a VD the following is to be considered:

• The process of expanding a VD is very time consuming and has a negative impact on the overall server performance while the expansion process is ongoing!

• The larger the drives are the longer the expanding of a VD will take! 1)

• The more drives are added into an existing VD the longer it will take! 1)

• Once started, the expanding / migration of a VD can not be paused or stopped!• Is backing up the data, deleting a VD and recreating it with the new drive(s) and

restoring data faster or slower than expanding a VD?See also Chapter 3 Measurement examples.

• When adding drives ensure that the new drives to an existing VD have the same specifications as the drives that are already in that VD, for example SATA / SAS, SSD, rotational HDD, sector size, overall drive capacity, etc.

• The new drive must be in unconfigured good state• Make sure that all currently installed disk drives are in good health in order to avoid a

drive failure during VD expansion• Ensure that the latest device drivers and firmware for any RAID controller is installed• Ensure that all drives are on the latest code level• Overall it is strongly recommended to run the server on the latest code level before

initiating VD expansion

1) There are reports that VD expansion can take a couple of days or weeks to complete.

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Changing Cache Policy during VD migrationDuring VD expansion the cache policy will be changed from write back to write through. This can be checked with the StorCLI utility.

Before migration

During migration

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After migration has completed

These changes in the cache policy also explain to why it can take a considerable amount of time for the VD migration to complete. This change of cache policy is a safety net in order to reduce the likelihood of data loss, but it is not a guarantee that data loss will be avoided.

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Chapter 3 Measurement examples

Chapter 3 Measurement examplesThis chapter gives examples how long it takes to expand a VD by using the StorCLI utility from within an operating system.

Note: The data provided in this chapter is based on expanding a VD once to its new target size by using various migration rates with StorCLI. Each expansion was performed only one.

Influences on the expansion timeThe time it takes to expand a VD depends on a number of factors:

• The number of disk drives to be added to the VD• The size of the disks to be added to the VD• The sector size (512 vs 4096 bytes) of the drives• The type of drive interface, that is SATA (only 6 Gbps) vs SAS (6 or 12 Gbps)• The RAID controller interface speed, 6 Gbps vs 12 Gbps

System x3650 M4The IBM System x3650 M4 server has a plug in IBM ServeRAID M5110 RAID controller which has a 6 Gbps interface with a 1 GB Cache Memory installed. The installed operating system is Windows Server 2016.

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Figure 1 shows the results of the StorCLI commands when expanding the VD with one drive.

Figure 1: Adding a 300 GB drive to a RAID 5 VD

As can be seen the migration time was quite slow at the beginning and had a significant improvement at a migrate rate between 40 % to 50 %. Before this and after this the performance gain is quite minimal, nearly linear.

The drive sector size is 512 bytes.

Lenovo SR550The Lenovo SR550 server has a plug in ThinkSystem RAID 930-16i with 4GB Flash PCIe controller which has a 12 Gbps interface. The installed operating system is Windows Server 2016.

Figure 2 shows the results of the StorCLI commands when expanding a VD with one drive. Figure 3 shows the results of the StorCLI commands when expanding a VD with two drives.

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Figure 2: Adding a 300 GB drive to a RAID 5 VD

Figure 3: Adding two 300 GB drives to a RAID 5 VD

The migration time is for adding one drive is very close to the migration time when two drives are added to an existing RAID 5 VD. At the beginning the performance gain is quite steep at a

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migrate rate of between 10 % to 50 % and it very slowly improves after a migrate of 50 % almost looking like a linear progress.

The drive sector size is 512 bytes.

A final word to the resultsThe measurement results show a significant difference between a RAID controller with a 6 Gbps interface versus a RAID controller with a 12 Gbps interface.

Further the migration rate for two drives seems to be quite close but could in reality be significantly different. The tests were performed on servers that were idle during the expansion process.

The measurement results are only provided as illustration examples and are to be taken with caution as these were not taken from production servers.

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Chapter 4 Using StorCLI

Chapter 4 Using StorCLIFor additional information with respect to requirements, please refer to Chapter 2 Important Considerations before expanding a VD.

Lenovo provides the Broadcom StorCLI tools for managing and working with the RAID controllers and the storage devices attached to it. StorCLI is a powerful command line tool which Lenovo supports for the following operating systems:

• Windows Server• Red Hat Enterprise Linux• SuSE Linux Enterprise Server• VMware ESXi

For more information on the supported operating sytems check the download section of your server on the Lenovo DCG support site and also the Lenovo OS Interoperbility Guide .

Note: It is strongly recommended to launch in Windows a command prompt with local administrative privileges whilst in a Linux distribution a terminal session with root rights should be executed. Users of VMware ESXi should log on to the console with local root rights.

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Preparations before migration

Showing all RAID controllers installed

The following command will list all RAID controllers installed in a server and to which drives are attached to:

storcli show

Figure 4: "storcli show" command output example

Figure 4 shows an output example of the storlci show command. It shows two RAID controllers installed in the server – controller (Ctl) 0 is the ServeRAID M5110e located on the server’s system board and a ServeRAID M5110 PCI controller is installed.

There are six drives (Pds) attached to the ServeRAID M5110 controller, two Drive Groups (Dgs) and two Virtual Drives (VDs, that is RAID arrays) have been configured.

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Displaying more information for a specific RAID controller

In order to obtain more detailed information the command

storcli /cx show all

needs to be executed. The x represents the controller number starting at 0 for the first controller and ending at 3 for the fourth and last controller. In Figure 5 an example output is given for the RAID controller 1 after executing the command storcli show.

Note: Since the output of the command

storcli /cx show all

is very long it is strongly recommended to redirect the output to a text file and to view that text file with an editor.

Example command for redirecting the output for RAID controller 1:

storcli /c1 show all > all_raid_controller_information.txt

The command issued is

storcli /c1 show all

The result is illustrated in Figure 5.

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Figure 5: "storcli /c1 show all" output at the beginning

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There are three areas of interest -

1. TOPOLOGYThe Topology section, see Figure 6 as an example, shows which drives are installed and assigned to what RAID level volume and some other information.

Figure 6: TOPOLOGY section

The areas of interests are:• EID:Slot which gives the enclosure ID, here 252, and the slot number in which the

drive is installed in• Type shows the RAID level and which drive is assigned to a specific RAID

volume, for example the drives in slots 5 and 6 of enclosure 252 are assigned to a RAID 1 volume

• Size shows the RAID volume size and the size of each drive

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2. VD LISTThe VD LIST, that is the virtual drive list, see Figure 7 as an example, shows some important information on already existing VDs on a specific RAID controller.

Figure 7: VD LIST information

The areas of interest are:• DG/VD shows all Drive Groups (DG) and Virtual Drives (VD). This shows how

many DGs and VDs exist on that RAID controller• TYPE shows on what RAID level that DG or VD is• Cache shows the cache policy set for a specific VD

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3. PD LISTThe PD LIST shows what physical devices (PD), that drives, are managed by the controller, see Figure 8 as an example.

Figure 8: Physical Drives and their curent state

The areas of interest are:• EID:Slt which shows the Enclosure ID and the slot number, but only those slots

where a drive is installed in• State the state of a drive, e.g. Onln (Online) or UGood (unconfigured good)

Note: A drive must be in UGood (unconfigured good) state in order to be added to an existing VD.

Changing a drive to Ugood

If the drive is brand new and has not been used its status may be JBOD (Just a Bunch Of Drives). In order to change a drive to unconfigured good the following generic command needs to be issued:

storcli /cx [/ex] /sx set good [force]

The parameters mean the following:

cx RAID controller, x is a value between 0 and 3

ex Enclosure ID, this parameter is optional

sx Slot number

force Force the drive status change, this parameter is optional

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If the drive in slot 4 in Figure 8 was shown as JBOD then the complete command to change the drive from JBOD to unconfigured good would be:

storcli /c1 /e252 /s4 set good

Additionally the parameter force can be added at the end of the above command.

Adding drive(s) to a VDThe process to add one or more drives to a VD is called migration.

Preparing for migration

It is recommended to first set the desired migrate rate with the command

storcli /cx set migraterate=<value>

where the parameters mean the following:


value 0 to 100 in percent

Notes: Whilst the migrate rate, that is value, is changed linear in percent, the actual performance change over time is non-linear. For further details see Chapter 3 Measurement examples.

Figure 9 shows the command for setting the migrate rate to 100 %.

Figure 9: Setting the migrate rate to 100 %

Initiating the migration

The generic command to add one or more drives is:

storcli /cx /vx start migrate <type=raidx> [option=<add|remove>drives=[e:]s|[e:]s-x|[e:]s-x,y] [Force]

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The better command is

storcli /cx /vx start migrate <type=raidlevel> [option=<add | remove> drives=<e1:s1,e2:s2 ...> ]


vx VD number starting at 0

raidxrxraidlevel

RAID Level to convert to, see Table 1: Migration from RAID level to RAID level for more details

add|remove Add to or remove from the VD the drive(s)

e:s Enlcosure ID:Slot ID

s-x Slots s to x

s-x,y Slots s to x and y

e1:s1,e2:s2 Enclosure ID1:Slot ID1,EnclosureID2:Slot ID2

Force Force the migration process

Table 1: Migration from RAID level to RAID level

Initial RAID Level Migrated to RAID Level

RAID 0 RAID 1

RAID 0 RAID 5

RAID 0 RAID 6

RAID 1 RAID 0

RAID 1 RAID 5

RAID 1 RAID 6

RAID 5 RAID 0

RAID 5 RAID 6

RAID 6 RAID 0

RAID 6 RAID 5

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Note: It is possible to migrate to the same level as the initial RAID level. For example if the initial RAID level is RAID 5 then this is a correct command:

storcli /cx /vx start migrate type=r5 [option=<add | remove> drives=<e1:s1,e2:s2 ...> ]

Figur es 10 and 1 1 show working migrate commands for adding one or two drives to an existing RAID 5 VD.

Figure 10: Adding one drive to an existing RAID 5 VD

Figure 11: Adding two drives to an existing RAID 5 VD

Checking migration progress

After issuing the migration command the storcli utility will quit and not display anything else. This means that users can not check the progress of the migration. The storcli utility allows to manually check the progress of the migration with the follwing command:

storcli /cx /vx show migrate


vx VD number starting at 0

Figure 1 2 shows an output of the show migrate command.

Figure 12: Output example for the "show migrate" command

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Notes: • In order to get an output similar to the one in Figure 11 it is recommended to wait some 10 minutes after issuing migration command

• Whilst the Progress% output is accurate the Estimated Time Left is an estimate.

Task to complete after migration finished

Once the show migrate command shows that the migration has finished, see Figure 13, then the following tasks need to be completed:

• Reboot the host server so that the bigger VD is recognised• Expand the operating system’s file system to cover the entire, larger VD

Chapter 6 Extending the file system shows this for a Windows operating system.

Figure 13: The "show migrate" command indicates that the migration has completed

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Chapter 5 ThinkSystem servers migration methods

Chapter 5 ThinkSystem servers migration methodsThe Lenovo ThinkSystem servers offer two alternative methods for adding drives to an existing to an existing Virtual Drive. For additional information with respect to requirements, please refer to Chapter 2 Important Considerations before expanding a VD .

These two alternative methods are:

• Using the server’s uEFI text interface • Using the servers’s LXPM (Lenovo Xclarity Provisioning Manager), a graphical interface

Both uEFI and LXPM provide similar functions as the StorCLI tool does.

Reconfiguring LXPM to boot into uEFI text mode1. Power on the server or reboot it into System Setup by pressing during server startup

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2. Wait until Lenovo XClarity Provisioning Manager, LXPM, has loaded

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3. Once LXPM has loaded click on UEFI Setup

4. Click on System Settings

5. Click on the arrow down symbol on the right of <F1> Start Control and select from the drop down menu the entry Text Setup

6. Save the selection

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7. Click on Yes in order to confirm that the changes are saved

8. Wait until the changes have been saved

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9. Click on Exit UEFI Setup and confirm this by clicking Yes

10. The server will now reboot. Press in order to enter the text uEFI setup

Reconfiguring uEFI text mode to boot into LXPMBoot the server via into the uEFI text interface:

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1. Navigate to System Settings and press

2. On <F1> Start Control press on Text Setup

3. A pop up menu shows three entries

The entries Auto and Tool Suite – see content of the green frame in the above screen shot - can be selected in order to reconfigure the server that LXPM will be started and the next boot via

4. In this example Auto will be selected. In order to activate this selection press

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5. Once Auto has been selected press s in order to get back to the System Configuration

and Boot Management Menu

6. Navigate to Save Settings and press

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7. The settings are being saved

8. Navigate to Exit Setup Utility and press

9. Press Y in order to confirm in order to exit from the uEFI text up

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10. The server will now reboot

uEFI text interfaceFor information on how to enable the uEFI text interface refer to the chapter Reconfiguring LXPM to boot into uEFI text mode.

For better visibility the screen shots from the uEFI text interface have been reduced to the to only display the essential information. This means that the white frame with the Lenovo logo has been removed thus improving the readability significantly. See below screen shots as an example:

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Changing drive status

A new drive may be in JBOD mode. In order to add a drive into VD, it has to be in unconfigured good status.

1. After booting the server into text uEFI select from the main menu System Configuration

and Boot Management the entry System Settings and press

2. Select Storage and press

3. Select the RAID controller to which the new drives are attached to that will be migrated into the existing VD

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4. Under the RAID controller menu navigate to the entry Configure and press

5. In the Configuration Management menu navigate to Make Unconfigured Good and press

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6. Either navigate to each drive that should be changed from JBOD to Unconfigured good and add it manually by pressing the space bar in the [ ]

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or select all drives by navigating to Check All and pressing

7. Once the desired drive(s) have been selected press on OK

8. In the Warning menu press the space bar at [ ] for confirming the selecting and enabling the Yes selection

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9. Navigate to Yes and press

10.In the Success windows press on OK

11.Back in the Configuration Management menu press s to get out of this menu

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Expanding a VD

Note: By default with ThinkSystem Series servers, pressing will open the Lenovo XClarity Provisioning Manager (LXPM) GUI. Refer to the section Reconfigur ing LXPM to boot into uEFI text mode for instructions on how to modify the settings and allow users to open the UEFI Setup text interface.

1. Power on or reboot the server2. When the ThinkSystem logo appears, press to open the UEFI Setup text interface

3. Once in the uEFI text interface navigate to "System Settings" and press [Enter]

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4. Navigate to "Storage" and press [Enter]

5. If required, select the correct RAID controller. Press [Enter] to get to the RAID controller settings

6. Navigate to "Main Menu" and press [Enter]

7. Navigate to “Virtual Drive Management” and press [ENTER]

8. Select the VD that will be expanded end press [ENTER]

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9. Navigate to “Select Operation” and press [ENTER]

10. Scroll down to “Reconfigure Virtual Drives” and press [ENTER]

11. Navigate to “Go” and press [ENTER]

12. If needed now the RAID level can be changed by pressing [ENTER] on the displayed RAID level of the “New RAID Level” selection

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For additional information on RAID level conversion see Table 1: Migration from RAID level to RAID level

13. Navigate to “Chose the Operation” and press [ENTER]

14. Press [ENTER] on the “Add Drives” option

will show only the option to add drives

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15. Either select the drives individually that are to be added to the RAID volume by navigating to the drive entry and press [ENTER]

or navigate to “Check All” to add all available drives to a RAID volume

Note that now all drives show an ‘X’ indicating that they are selected

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16. Navigate down to “Apply Changes” and press [ENTER]

17. Press [ENTER] at “Confirm” so that the ‘X’ is displayed

18. Navigate to “Yes” and press [ENTER]

19. Press [ENTER] at “OK”

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20. Navigate to “Start Operation” and press [ENTER]

21. Press [ENTER] at “OK”

22. Back in the “Reconfigure Virtual Drives” menu press [ESC]

23. Navigate to “Virtual Drive Management” and press [ENTER]

24. The progress of the reconstruction will be displayed

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25. After the reconstruction has completed the new size and status of the RAID volume will be displayed

26. The server can now be rebooted

Note: At step 25 the server can be rebooted as follows:

• Press [ESC] until back the “System Configuration and Boot Management” menu is displayed

• Select “Exit Setup Utility”• When prompted to save the changes before exiting the Setup Utility select “Y” to save

the changes before rebooting

Rebooting the server into the Operating System has no impact on the reconstruction process and this process will continue until completed after booting into the Operating System.

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Lenovo XClarity Provisioning ManagerFor information on how to enable the uEFI text interface refer to the chapter Reconfiguring uEFI text mode to boot into LXPM.

Power on or reboot the server. At the prompt press in order to boot into the LXPM.

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Changing drive status

A new drive may be in JBOD mode. In order to add a drive into VD, it has to be in unconfigured good status.

1. After booting the server into the Lenovo XClarity Provisioning Manager, LXPM, graphical interface

2. click on UEFI Setup

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4. Click on Storage

5. Click on the RAID controller to which the JBOD drive(s) is / are attached to

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Changing drives individually from JBOD to Unconfigured Good

In order to get to this menu follow the steps of the chapter Changing drive status.

1. Click on Main menu

2. Click on Drive Management

3. Select the drive that needs to be changed from JBOD to Unconfigured Good

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4. In the Operation drop down menu select Make Unconfigured Good

5. Click on Go

6. Click on OK

7. Click on Save

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8. Click on Yes in order to confirm that the changes are to be saved

and wait until changes have been saved

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9. Click on Back

10. Click on Back again

11. Click on Drive Management

in order to see the changed drive status

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Repeat steps 3 to 11 of this section to change any other drive from JBOD to Unconfigured Good.

Changing more than one drive from JBOD to Unconfigured Good

In order to get to this menu follow the steps of the chapter Changing drive status.

1. Near the bottom of this page click on Configure

2. Click on Make Unconfigured Good

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3. Either select the drives individually by clicking into the box on the right of each drive

or select all drives by clicking on Check All

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4. Click on OK

5. Click into the box right to Confirm and then click on Yes

6. Click on OK

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7. Click on Save

Expanding a VD

1. In the main menu of the LXPM click on UEFI Setup


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3. Click on Storage

4. Click on the RAID Controller where the VD is attached to that needs expanding

5. Click on Main Menu

6. Click on Virtual Drive Management

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7. Click on the RAID volume that is to be expanded

8. In the Operation drop down menu select Reconfigure Virtual Drives

9. Click on Go

10. If the RAID level is to be changed, click on the drop down menu of New RAID Level

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and chose the desired RAID level

For the purpose of this document the RAID level will not be changed and remains as RAID 5See Table 2: Migration from RAID level to RAID level for information from which RAID level to which RAID level can be migrated

11. Click on Chose the Operation

12. Make sure that the Add Drives option is selected in the Chose the operation you want to

perform drop down menu

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13. Either select the drives to be added to the existing RAID volume individually

14. or click on Check All in order to add all drives to the existing Virtual Drive

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15. Click on Apply Changes

16. Click the box right to Confirm and then click on Yes

17. Click OK

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18. Click on Start Operation

19. Click OK

and wait until the operation is completed

Note: It is not necessary to wait in step 19 for the Virtual Drive expansion to complete. The server can be rebooted into the Operating System as doing so has no impact on the reconstruction process and this process will continue until completed after booting into the Operating System.

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Table 2: Migration from RAID level to RAID level

Initial RAID Level Migrated to RAID Level

RAID 0 RAID 1

RAID 0 RAID 5

RAID 0 RAID 6

RAID 1 RAID 0

RAID 1 RAID 5

RAID 1 RAID 6

RAID 5 RAID 0

RAID 5 RAID 6

RAID 6 RAID 0

RAID 6 RAID 5

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Chapter 6 Extending the file system


Note: After the RAID volume has been expanded with the StorCLI utility most operating systems require a server reboot in order to recognise the changed RAID VD size. Newer releases of VMware ESXi only require extending the file system.

Windows ServerOnce StorCLI has completed the migration process, that is expanding the Virtual Drive, start the Windows Server Disk Managment tool for example via command line with the command diskmgmt.msc. The result will be looking similar to the below image, not showing the expanded drive.

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After the server has been rebooted the expanded volume can be seen:

Expanding the file system

1. Right click on the drive for which the file system should be expanded and click on Extend Volume...

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2. Click on Next

3. Click Next

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4. Click on Finish

5. Once the expansion has been completed the new size will be displayed

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Chapter 7 Situations where the expansion of a VD will fail

Chapter 7 Situations where the expansion of a VD will failThere are a number of reasons to why expanding a Virtual Drive will fail. Failures can be observed when the Virtual Drive is degraded, for example when a drive failed and has not been replaced or when a failed drive has been replaced and a rebuild is taking place.

All drives are in a RAID volume support Data Protection (T-10 Protection Information) but the new drives do not. In this case the Data Protection needs to be turned off.

Another reason that a VD expansion will fail is when puncturing bad blocks are taking place. In order to resolve puncturing bad blocks, refer to Tech Tip HT504153 "Puncturing bad block: Recovering ServeRAID unrecoverable medium errors - Lenovo Servers, Lenovo ThinkSystem and IBM Systems" per https://datacentersupport.lenovo.com/solutions/ht504153.

Two more common reasons for VD expansion to failBesides the technical reasons that virtual drive can fail there are two common reasons to why a VD expansion will fail:

• RAID volume has been created that does not use the full capacity of all drives • RAID volume has been created with mixed size of drives

RAID volume is not using the full capacity of all drives

It is possible to create with a set of drives of the same capacity a RAID Virtual Drive that does not use the full capacity of all drives.

The below figure illustrates a RAID 5 volume where only part of the drive capacity is used to create a RAID volume:

The blue area represents the RAID 5 volume, the grey area the unused space.

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As an example:

If in the above example four disk drives are used with each having a capacity of 1 TB but a RAID Virtual Drive has been created using only 500 GB of each drive capacity then the overall RAID 5 Virtual Drive capacity will be approximately 2000 GB of which about 1397 GB can be used for data storage.

Such a RAID volume can not be expanded when drives of the same capacity, e. g. 1 TB, are added to the server.

If the full capacity of each drive were used, that is 1 TB, then the overall capacity would be approximately 4 TB of which about 2.7 TB can be used for data storage.

RAID Virtual Drive created with drives of different capacity

It is possible to create a RAID Virtual drive with drives of different capacity. The below figure gives an example of such a set up:

As an example the Disks 0, 1, and 2 have a capacity of 500 GB whilst Disk 3 has a capacity of 300 GB. The blue area represents the RAID 5 volume, the grey area the unused space.

This RAID 5 volume has in this example a capacity of approximately 1200 GB of which about 838.2 GB can be used for data storage.

Replacing the 300 GB Disk 3 with another Disk with 500 GB capacity will lead to a RAID rebuild with the same capacity as if the 300 GB Disk were still part of the RAID Virtual drive. In other words the resulting RAID 5 Virtual Drive would be looking like as shown below:

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Again, the blue area represents the RAID 5 volume, the grey area the unused space.

This RAID volume can not be expanded.

Displays when a RAID volume can not be expandedDepending on the method chosen to expand the RAID Virtual Drive different messages or displays will be shown.

StorCLI

The StorCLI utility will display an error message that Virtual Drive can not be expanded as the below example illustrates:

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Lenovo XClarity Provisioning Manager, LXPM

LXPM will not show the option to Reconfigure Virtual Drives:

If the RAID volume was properly set up to use the full capacity of all same sized disk drives the option would be displayed:

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Text uEFI

Text uEFI interface will not show the option to Reconfigure Virtual Drives:

If the RAID volume was properly set up to use the full capacity of all same sized disk drives the option would be displayed:

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Only possible solutionThe only solution in such a situation – under the assumption none of the technical issues explained earlier apply – is to:

1. Backup all data2. Delete the Virtual Drive3. Create the Virtual Drive with the additional disk drives4. Re-install the Operating System if required5. Restore all data

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Appendix A Sources

Appendix A SourcesThe RAID drive images from Chapter 7 are modified images from the Wikipedia article “Standard RAID levels”.

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https://en.wikipedia.org/wiki/Standard_RAID_levels

ht509076 how to add drives to a raid array

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