Fixing a degraded RAID

Rebuilding the degraded RAID volume will vary depending on the level of RAID.

RAID 1, RAID 5 & RAID 10

Fault tolerance is provided through RAID 1, RAID 5 & RAID 1o by mirroring or parity. If a single disk fails, you can replace it and the RAID will rebuild itself automatically. This is know as ‘hot-swapping’. You can check on the rebuilding process in the Storage Pool or Static Volume.

If you need to manually rebuild the RAID – often associated with is hardware or rack based controllers.


  • Replace the failed hard drive and log into the NAS through a web browser
  • Go to Storage > Storage/Snapshots
  • Select your Storage Pool or Static Volume and click Manage
  • Choose the degraded RAID group and click Manage > Configure Spare Disk
  • Choose the new hard drive and click Apply


Unlike the RAID levels above, RAID 0 doesn’t come with redundancy. Should a single disk fail, all the data is lost. Firstly stop writing data and don’t be tempted to rebuild the RAID 0 straight away. Professional data recovery services or software will be necessary.

What are the symptoms of a RAID failing?


  • RAID controller errors
  • Server crash
  • Read/ write errors
  • Partition loss
  • Data corruption

Preventing RAID failure

Hard drive failures are generally the most common cause of RAID failures, so it makes sense to ensure your hard drives are healthy. Use S.M.A.R.T disk monitoring to identify any issues and do not ignore any warnings from your RAID controller If the RAID array fails, stop using the RAID volumes immediately and don’t be tempted to change the order of the disks.

Online Price Calculator



Michael Jones Data Recovery Specialists   

Michael Jones, Technical Director

Further reading

Drobo and BeyondRAID data recovery

Seagate NAS rescue & repair

How to avoid RAID data recovery