D-Link DSN-6120 User Manual - Page 80
Advanced operations
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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. 80