HP 3100ES - Smart Array RAID Controller User manual

RAID 1(+0): breaking mirrors and rebuilding

drives

How to, 4th edition

Abstract.............................................................................................................................................. 2

Introduction......................................................................................................................................... 2

Splitting a mirrored array using the Array Configuration Utility.................................................................. 3

Recombining a split mirrored array using the Array Configuration Utility .................................................... 4

Breaking a mirror and rebuilding the array using the manual method ........................................................ 5

Reverting to a previous copy of a mirrored set using the manual method .................................................... 7

For more information............................................................................................................................ 9

Call to action ...................................................................................................................................... 9

Abstract

This paper explains two methods for safely breaking a RAID 1(+0) mirror and rebuilding drives in

configurations with RAID1 (+0) volumes. The first method, using the HP Array Configuration Utility

(ACU) split mirror feature, is available only while a server is offline and only for select controller

models that may also require a valid HP Smart Array Advanced Pack license. All HP Smart Array

controller models support the legacy method for manually breaking a RAID 1(+0) mirror.

Introduction

When using a configuration with RAID 1(+0) logical drives attached to an HP Smart Array controller,

it may become necessary to break a mirror and rebuild the drives for one of several reasons:

•When a drive in a RAID 1(+0) volume fails, the controller essentially breaks the mirror. An

administrator subsequently can regain fault tolerance and resynchronize the mirrored drives by

removing the failed drive(s) and replacing them with new drive(s).

•As a precaution against a future failure situation, an administrator can break a mirror for system

backup: Using the Array Configuration Utility (ACU),the administrator can remove half of the

mirrored drives and store them for use as system backup.The administrator can then replace the

removed drives with new drives and allow the controller to automatically rebuild the new drives to

restore fault tolerance. Reverting to a previous backup is more complex and is explained later in

this paper.

•When increased capacity is required, an administrator can replace half of the drives in a RAID 1 or

RAID 1+0 array with larger capacity drives and rebuild the new drives. Afterwards, the

administrator can replace the other half of the drives and allow them to rebuild in the other

direction. Once all drives in the array are of larger capacity, the administrator can use the ACU to

increase the logical drive size or to configure additional volumes.

•When troubleshooting drives or testing software configurations, an administrator can use half the

mirrored drives as a backup copy and then revert to that backup copy if a software configuration

(for example, an operating system patch) is unsuccessful.

HP provides two utilities for configuring an array on a Smart Array controller:

•ORCA—A simple utility used mainly to configure the first logical drive in a new server before the

operating system is loaded

•ACU—An advanced utility for performing many complex configuration tasks

Table 1 lists the Smart Array controllers and the methods each currently supports.

Table 1. HP Smart Array controllers supporting ACU and manual methods of breaking RAID 1(+0) mirrors

Supported Controllers ACU Method Manual Method

Smart Array P212, P410, P410i, P411,

P712

(ACU method requires Advanced Pack

License)

x x

Smart Array E500, P400, P400i,

P700m, P800

x x

Smart Array E200, P600

x x

Smart Array 6i, 641, 642, 6402, 6404

(ACU method requires firmware version

2.58 or higher)

x x

Integrated Smart Array x

SMART-2/P, SMART-2/E, SMART-2SL,

SMART-2DH

Smart Array 221, 3100ES, 3200, 431,

4200, 4250ES, 5i, 5i Plus, 532, 5312,

5302, 5304

Splitting a mirrored array using the Array Configuration

Utility

This functionality, available in some controller models and ACU versions, splits an array that consists

of one or more RAID 1(+0) logical drives into two identical new arrays consisting of RAID 0 logical

drives. This functionality is useful when replicating a configuration or building a backup before

performing a risky operation. Note that this is a bit different from the manual method, in which the

volumes remain in their original RAID 1 or RAID 1+0 configuration after being split. Also note that

using the ACU does not require splitting other arrays attached to the controller at the same time. The

Array Configuration Utility will show the Split Mirror task as an available option only under all of the

following conditions:

•Both versions of ACU being used and the selected controller support the action.

•The server is offline.

•Any applicable Smart Array Advanced Pack keys have been successfully installed.

IMPORTANT

You cannot split an array if it contains logical drives in RAID 0,

RAID 5, RAID 6, RAID 50, or RAID 60 configurations.

NOTE

You can split or re-mirror an array only when the server is

offline.

To split a mirrored array using the ACU, complete the following steps:

1. Take the server offline.

2. Insert the CD or bootable USB drive that contains the ACU (typically SmartStart) into any available

media drive.

3. Restart the operating system.

4. Select the HP ACU selection within the Maintenance Operation menu.

5. In the selection panel, select Array Configuration and Diagnostics.

6. In the Configuration drop down menu, select the applicable controller.

7. Highlight or select the desired logical drive.

8. In the Select a Task panel, click Split Mirrored Array.

9. Click OK.

10.When ACU has finished splitting the array, you will see both logical drives in the Maintenance

Operation menu.

11.Shut down the system.

12.With power off, remove the physical drives that are included in one of the new arrays.

IMPORTANT

If you do not remove one of the arrays, the operating system will

be unable to distinguish between the two new arrays after the

operating system has been restarted (next step) because the

arrays will be identical.

13.Restart the operating system.

Recombining a split mirrored array using the Array

Configuration Utility

To re-mirror an array using ACU, complete the following steps:

1. Take the server offline.

2. Insert the CD or bootable USB drive that contains the ACU (typically SmartStart) into any available

media drive.

3. Restart the operating system.

4. Select the HP ACU selection within the Maintenance Operation menu.

5. Select the drive controller that contains the array to be re-mirrored.

6. In the Configuration View panel, select the array to use as the source array in the recombined

mirrored array.

7. In the Select a Task panel, click Re-Mirror Array.

8. Select the array that is to be mirrored to the source array. (This is usually the array that was

previously split out of the original mirrored array. However, it can be another array of the correct

size.)

CAUTION

All data on the second array will be destroyed.

9. Click OK.

10.When ACU has finished updating the configuration, restart the operating system. The Smart Array

controller will use the rebuild process to synchronize the mirrored drives. You can boot the

operating system during the rebuild process, but the logical drive will not be fault-tolerant until the

rebuild is complete.

NOTE

The drive-online LED will blink during the rebuild synchronization

process. When it stops blinking and turns solid green, the

rebuild is complete. A 300-GB SAS (3.5” 15K) drive can take

up to 2 hours to rebuild a mirrored array (depending on the

number of IOPS the server is submitting to the controller).

For more information or to download the Array Configuration Utility, refer to this URL:

http://h18004.www1.hp.com/products/servers/proliantstorage/software-management/acumatrix/index.html

Breaking a mirror and rebuilding the array using the

manual method

CAUTION

Use the following procedure for configurations with only one

array on the controller. If multiple arrays are configured on a

single controller, all arrays (and consequently all logical drives

within each array) must be broken and restored together.

Because of the added complexity, this method of creating a

quick backup of the logical drives is strongly discouraged in

configurations with multiple arrays per controller.

A RAID 1 mirror can be broken simply by removing a drive while the server is online. However, to

preserve the data on drives being removed, it is necessary to shut down the system first. If the

removed drives will be used to restore the system, or if the data on the drives will be required for any

reason, follow these steps exactly to break a mirror:

1. Verify that the controller is configured with RAID 1 (or RAID 1+0) logical drives only.

2. Shut down the operating system (to ensure a clean file system shutdown).

3. Shut down the server.

4. With the power off, remove one half of the drives created by the mirror (the backup). Be sure to

label each of the removed drives with its respective drive bay number, and store these drives in a

safe place.

NOTE

For two-drive configurations, just remove one drive. For RAID 1+0

configurations, the first n/2 drives are always mirrored to the

second n/2 drives (unless drives have been physically reordered

using Offline Drive Movement).Do not remove drives that are

mirrored to one another.

5. Restart the operating system with the remaining half of the drives that were created by the mirror.

6. During boot-up, a message will indicate that the removed drives are not responding (Figure 1).

Press F2 to fail the missing drive(s) and continue in recovery mode. All drives on the controller will

remain disabled until you press F2. If you press F1 by mistake, simply reboot again and press F2

to fail the drives.

Figure 1. Boot-up message indicating that the logical drive is still available but missing physical drives

NOTE

If the logical drive is failed at this point and the system will not

boot, most likely two drives that were mirrored to one another

have been removed. If this occurs, shut down the system,

reinstall all drives, and turn the system back on. The drives that

were mirrored to one another will be marked okay and all data

should still be intact. Start again at step 1, being careful not to

remove any drives that are mirrored to one another.

7. Insert a new drive into the open drive bay and the array rebuild should start automatically. If the

rebuild does not start automatically, reboot and press F1 to enable rebuild at the 1786 Recovery

Needed POST message prompt.

NOTE

The drive-online LED will blink during the rebuild process. When

it stops blinking and turns solid green, the rebuild is complete. A

300-GB SAS (3.5” 15K) drive can take up to 2 hours to rebuild

a mirrored array (depending on the number of IOPS the server

is submitting to the controller).

8. After the rebuild is complete, proceed with the operating system boot.

Rebuilding the array will bring the array back into a fault-tolerant state. If the mirror was broken

simply to try an operating system patch, it is normally not necessary to make the array fault-tolerant

again until after the patch is tested.

Reverting to a previous copy of a mirrored set using the

manual method

This method works only if the mirrored set was originally broken using the manual method (not if the

ACU method was used to break the mirror).

CAUTION

HP strongly recommends that before inserting the backup drives

(in step 1 below), you verify that all drives from the current array

have been removed. Any drive that became part of the array

during a rebuild process can OVERWRITE the BACKUP drive.

Be especially careful in using hot spares, where the rebuild may

have happened automatically and it is unclear whether another

drive is now part of the array. To simplify this process, remove

any spares before breaking the mirror and reinstall the spares

only after the array is rebuilt.

To revert to a previous copy of a mirrored set, complete the following steps:

1. With the system off, remove all drives from the array, and insert the drives containing the backup

data (the original image on the array). The backup drives must be installed in their original

locations. (If it is unclear which drive bay a backup drive came from, insert the drive into one of

the drive bays where the array was created and continue with caution; it may be necessary to

move drive if a logical drive is not detected during boot-up).

2. Restart the system with only the backup drives installed. If no logical drives are found during

boot-up (Figure 2), a drive is most likely in the wrong drive bay. If that occurs, turn off the server,

remove the drive, and place it into another available drive bay; then power the server back on

again.

Figure 2. Boot-up message indicating no logical drives were found and that the backup drives are probably in

the wrong drive bays

3. During boot-up, the message will indicate that the drives are not responding (Figure 2). Press F2 to

fail the missing drive and continue with one drive in recovery mode.

4. Insert the drive to be overwritten into the open drive bay, and the array rebuild should start

automatically. If the rebuild does not start automatically, run the Array Configuration Utility to

initiate the rebuild.

CAUTION

It is critical that the drives to be overwritten are hot inserted;

they must not be installed while the server is powered off.

NOTE

The drive-online LED will blink during the rebuild process. When

it stops blinking and turns solid green, the rebuild is complete. A

300-GB SAS (3.5” 15K) drive can take up to 2 hours to rebuild

a mirrored (depending on the number of IOPS the server is

submitting to the controller).

5. It is recommended that once the rebuild is complete, proceed with the operating system re-boot to

ensure fault-tolerance with the logical drive.

For more information

For additional information, refer to the resources listed below.

Resource description Web address

Business Support Center for HP Array

Configuration Utility

http://h20000.www2.hp.com/bizsupport/TechSupport/Home.jsp?la

ng=en&cc=us&prodTypeId=18964&prodSeriesId=468780

Configuring Arrays on HP Smart

Array Controllers Reference Guide

http://h20000.www2.hp.com/bc/docs/support/SupportManual/c00

729544/c00729544.pdf

Call to action

Send comments about this paper to [email protected].

herein is subject to change without notice. The only warranties for HP products and

services are set forth in the express warranty statements accompanying such

products and services. Nothing herein should be construed as constituting an

additional warranty. HP shall not be liable for technical or editorial errors or

omissions contained herein.

TC090801HT, August 2009

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