RAID Rebalancing

Rebalance re-stripes RAID data to improve performance or migrate data from specific disks Rebalance also recognizes orphaned pages and returns them to the free pool.

To re-stripe data, from the Storage Management menu, choose Disks > Rebalance RAID Devices.

When considering whether to move a RAID Device, there are three options based on the RAID Device Score. The highest of these scores determines the decision.

• Current Score Highest: No need to move -- presently no better alternative.
• Replacement Score Highest: Move to permanent space. Replacement Score is high when there is considerable available storage, possibly due to the addition of drives since the RAID devices were created, or storage availability from other RAID Device consolidation.
• Replacement Overlay Score Highest: Move the RAID Device to temporary space, delete source RAID Device, then move it to its permanent space. Addresses the notion: “Can we optimize the RAID device with the storage we have?”. This process moves from the temporary space to replacement score space as appropriate.

Rebalancing takes longer when using temporary space. Rebalancing has the potential to deadlock when moving some RAID devices. Rebalancing moves the lowest scoring RAID Devices first; beginning with the smallest RAID Devices. Rebalancing may take several days. Rebalancing can be scheduled to run over night or weekend.

See the Compellent User Guide for additional information and illustrations of RAID Rebalancing.