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A disk, to be added to a RAID set, must be in normal mode (not failed), free (not spare, in a RAID set, or
passed through to host) and must have at least the same capacity as the smallest disk capacity already in the
RAID set.
Capacity expansion is only permitted to proceed if all volumes on the RAID set are in the normal status.
During the expansion process, the volume sets being expanded can be accessed by the host system. In
addition, the volume sets with
RAID level 1, 10, 3, 5 or 6 are protected against data loss in the event of
disk failure(s). In the case of disk failure, the volume set changes from "migrating" state to
"migrating+degraded" state. When the expansion is completed, the volume set would then transition to
"degraded" mode. If a global hot spare is present, then it further changes to the "rebuilding" state.
The expansion process is illustrated as following figure.
RAID controller redistributes the original volume set over the original and newly added disks, using the same
fault-tolerance configuration. The unused capacity on the expand RAID set can then be used to create an
additional volume set, with a different fault tolerance setting (if required by the user.)
Online RAID Level and Stripe Size Migration
•
For those who wish to later upgrade to any RAID capabilities, a system with online RAID level/stripe size
migration allows a simplified upgrade to any supported RAID level without having to reinstall the operating
system.
The RAID controllers can migrate both the RAID level and stripe size of an existing volume set, while the
server is online and the volume set is in use. Online RAID level/stripe size migration can prove helpful during
performance tuning activities as well as when additional physical disks are added to the RAID controller. For
example, in a system using two drives in RAID level 1, it is possible to add a single drive and add capacity and
retain fault tolerance. (Normally, expanding a RAID level 1 array would require the addition of two disks).
A third disk can be added to the existing RAID logical drive and the volume set can then be migrated from
RAID level 1 to 5. The result would be parity fault tolerance and double the available capacity without taking
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