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Abstract; Introduction - HP 3100ES - Smart Array RAID Controller Manual

Raid 1(+0): breaking mirrors and rebuilding drives



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.


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
Array Configuration Utility
mirrored drives and store them for use as system backup
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.
the administrator can remove half of the
The administrator can then replace the

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