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
x
Smart Array 221, 3100ES, 3200, 431,
4200, 4250ES, 5i, 5i Plus, 532, 5312,
5302, 5304
x
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].
© 2009 Hewlett-Packard Development Company, L.P. The information contained
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