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Qsan Document – User Manual
Advanced Operations
5
Volume Rebuild
If one physical disk of the RAID group which is set as protected RAID level (e.g.: RAID 5, or RAID 6)
fails or has been removed, then the status of RAID group will be changed to degraded mode. At
the same time, the system will search the spare disk to execute volume rebuild the degraded RAID
group into complete one.
There are three types of spare disks which can be set in
Physical Disks
:
Dedicated Spare
: The hard drive has been set as dedicated spare of a RAID group.
Local Spare
: The hard drive has been set as local spare of the enclosure.
Global Spare
: The hard drive has been set as global spare of whole system.
The detection sequence is the dedicated spare disk as the rebuild disk first, then local spare disk
and global spare disk.
The following examples are scenarios for a RAID 6.
1.
When there is no global spare disk or dedicated spare disk in the system, The RAID group will
be in degraded mode and wait until there is one disk assigned as spare disk, or the failed disk
is removed and replaced with new clean disk, and then the Auto-Rebuild starts.
2.
When there are spare disks for the degraded array, system starts Auto-Rebuild immediately.
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 RAID
group is
Online
. Thus, it will not conflict with the online roaming feature.
3.
In degraded mode, the health of the RAID group is
Degraded
. When rebuilding, the status of
RAID group and virtual disk will display
Rebuilding
, the column
R%
in virtual disk will display
the ratio in percentage. After complete rebuilding, the status will become
Online
.
TIP:
The dedicated spare cannot be set if there is no RAID group or only RAID groups
with RAID 0 or JBOD level.