User manual

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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.
RAG362 controllers support Auto-Rebuild. The following is the scenario:
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. RAG362 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.
Sometimes, rebuild is called recover; they are the same meaning. The following table
is the relationship between RAID levels and rebuild.
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.
RAG362