DATOptic ARC-1680 Series - Manual (Page 168)

APPENDIX
168
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 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.
The SAS 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.)