Resolving Problems with RAID-5 Sets

Most problems with RAID-5 sets have to do with the intermittent or permanent failure of a drive. If one of the drives in the set goes offline or experiences temporary I/O problems, parity data cannot be properly written to the set and, as a result, the set's status will show as Failed Redundancy and the failed volume's status changes to Missing, Offline, or Online (Errors).

You must get all drives in the RAID-5 set online. If the status of the problem volume is Missing or Offline, make sure that the drive has power and is connected properly. You then must start Disk Management and rescan the missing drive by choosing Rescan Disks from the Action menu. When Disk Management finishes, right-click the drive, and choose Reactivate. The drive status should change to Regenerating and then to Healthy. If the volume doesn't return to the Healthy status, right-click the volume, and then click Regenerate Parity.

A status of Failed, Online (Errors), or Unreadable indicates I/O problems with the drive. As before, try rescanning the drive, and then try to reactivate the drive. The drive status should change to Regenerating and then to Healthy. If the volume doesn't return to the Healthy status, right-click the volume, and then click Regenerate Parity.

If one of the drives still won't come back online, you must repair the failed region of the RAID-5 set. Right-click the failed volume, and then select Remove Volume. You now must right-click an unallocated space on a separate dynamic disk with the same partition style-either MBR or GPT-and choose Repair Volume. This space must be at least as large as the region to repair, and it can't be on a drive that's already being used by the RAID-5 set. If you don't have enough space, the Repair Volume option is unavailable and you must free space by shrinking a volume, deleting other volumes, or replacing the failed drive.