Chapter 5 - Advanced Operations; Volume Auto-Rebuild - Overland Storage SnapSAN S1000 User Manual

Chapter 5

Volume Auto-Rebuild

SnapSAN S1000 supports the Auto-Rebuild feature. If one disk drive of a protected RAID
Group (for example, RAID 3, RAID 5, or RAID 6) either fails, is unplugged, or is removed,
then the status of RAID Group is automatically changed to degraded mode. The system then
searches for a spare disk to rebuild the group. It will first look for a spare disk dedicated to
the RAID Group, and then for a global spare disk.
The following examples are scenarios for a RAID 6 group:
• No dedicated or global spare disk drive – The RAID Group is set to degraded
mode and waits to start Auto-Rebuild until:
• There is a disk drive assigned as a spare disk drive (dedicated or global).
• The failed disk is removed and replaced with new disk drive. The new disk
If the newly added disk drive comes with information from an existing RAID Group on
it, the disk drive is marked as RS (reserved) and the system does not start the Auto-
Rebuild.
If the new disk drive does not belong to any existing RAID Group, it is marked as a FR
(Free) disk drive and the system starts the Auto-Rebuild.
If the failed disk drive is removed and then plugged back into the same slot, the
Auto-Rebuild will start running.
protection.
• Enough dedicated or global spare disks exist – The system starts the Auto-
Rebuild immediately. In RAID 6, if another disk failure occurs during rebuilding the
disk drives, the system will start the previous Auto-Rebuild process as well.
The Auto-Rebuild feature only works when the status of the RAID Group is Online. It
does not work with it Offline. That way, it does not conflict with the Online Roaming
feature.
While in degraded mode, the status of RAID Group is shown as Degraded. When rebuilding,
the status of RAID Group changes to Rebuild and the column R % on the Virtual Disks page
displays the rebuild ratio as a percentage. After the rebuilding is complete, the status
returns to Online.
NOTE: The Set Dedicated Spare option is not available if there is no RAID Group or the only RAID
This table shows the relationship between RAID levels and a rebuild (recovery):
10400310-003 01/2013
automatically becomes a spare disk to the original RAID Group.
Rebuilding the same failed disk may impact customer data if the status of
CAUTION:
disk is unstable. It is highly recommended not to rebuild a failed disk for better data
Groups are RAID 0 or expansion arrays. A dedicated spare disk cannot be set for a RAID 0 or
expansion array.
©2010-13 Overland Storage, Inc.
Advanced Operations
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