Online Capacity Expansion - Areca ARC-1110 User Manual

INTRODUCTION
the configuration settings in the event of controller failure. Array
roaming allows the administrators the ability to move a comple-
tele raid set to another system without losing RAID configuration
information or data on that raid set. So, if a server fails, the raid
set disk drives can be moved to another server with an identical
RAID card and the disks can be inserted in any order.

1.3.3.3 Online Capacity Expansion

Online Capacity Expansion makes it possible to add one or more
physical drives to a volume set without interrupting server op-
eration, eliminating the need to backup and restore after recon-
figuration of the raid set. When disks are added to a raid set,
unused capacity is added to the end of the raid set. Then, data
on the existing volume sets (residing on the newly expanded
raid set) is redistributed evenly across all the disks. A contigu-
ous block of unused capacity is made available on the raid set.
The unused capacity can be used to create additional volume
sets.
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 levels
1, 1E, 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 tran-
sitions 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 transitions to the "rebuilding" state.
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