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Chapter 5
Advanced operations
5.1
Volume rebuild
If one physical disk of the RG which is set as protected RAID level (e.g.: RAID 3, RAID 5,
or RAID 6) is FAILED or has been unplugged / removed, then the status of RG is changed
to degraded mode, the system will search/detect spare disk to rebuild the degraded RG to
a complete one. It will detect dedicated spare disk as rebuild disk first, then global spare
disk.
D-LINK IP SAN storage supports Auto-Rebuild. Take RAID 6 for example:
1.
When there is no global spare disk or dedicated spare disk in the system, The RG will
be in degraded mode and wait until (1) there is one disk assigned as spare disk, or (2)
the failed disk is removed and replaced with new clean disk, then the Auto-Rebuild
starts. The new disk will be a spare disk to the original RG automatically. If the new
added disk is not clean (with other RG information), it would be marked as RS
(reserved) and the system will not start "auto-rebuild". If this disk is not belonging to
any existing RG, it would be FR (Free) disk and the system will start Auto-Rebuild. If
user only removes the failed disk and plugs the same failed disk in the same slot
again, the auto-rebuild will start running. But rebuilding in the same failed disk may
impact customer data if the status of disk is unstable. D-LINK suggests all customers
not to rebuild in the failed disk for better data protection.
2.
When there is enough global spare disk(s) or dedicated spare disk(s) for the degraded
array, system starts Auto-Rebuild immediately. And in RAID 6, if there is another disk
failure occurs during rebuilding, system will start the above Auto-Rebuild process as
well. Auto-Rebuild feature only works at that the status of RG is "Online". It will not
work at “Offline”. Thus, it will not conflict with the “Online roaming” feature.
3.
In degraded mode, the status of RG is “Degraded”. When rebuilding, the status of
RG / VD will be “Rebuild”, the column “R%” in VD will display the ratio in
percentage. After complete rebuilding, the status will become “Online”. RG will
become completely one.
Tips
“Set dedicated spare” is not available if there is no RG or only RG of
RAID 0, JBOD, because user can not set dedicated spare disk to RAID 0 and
JBOD.
Sometimes, rebuild is called recover; they are the same meaning. The following table is
the relationship between RAID levels and rebuild.