EX2 Ultra - Replaced 1 disk - RAID Health Degraded after RAID Rebuild

My Cloud OS 5 Personal & Network Attached Storage My Cloud EX Series
1

I have a My Cloud EX2 Ultra NAS, almost 6 years old, and got a red light indicating a disk problem. The NAS is set up as a RAID 1 array of two 6TB disks. The dashboard said one of the disks is bad, so I bought a replacement. The bad disk was a 6TB WD WD60EFRX disk and I replaced it with a 6TB WD WD60EFPX disk.

I powered off the NAS, removed the old disk and inserted the new one, powered it back on and the dashboard said: “RAID Health: Rebuilding. Volume_1 is rebuilding.” The rebuild process took almost exactly 14 hours. Immediately after it was completed, the dashboard reported: “RAID Health: Degraded. One or more RAID volumes are degraded.”

The NAS dispatched an email to me, which said: “Volume 1 is degraded. Check the system’s drive status by running Disk Test in Settings / Utilities.” So I ran a “Quick Test”, and the result was:
Disk1 Passed - Quick disk test completed successfully.
Disk2 Passed - Quick disk test completed successfully.

I decided to just reboot the NAS, after which it seems the NAS decided to automatically restart the RAID rebuild process. I left it running again, and 14.5 hours later, there was the same outcome - RAID Health: Degraded.

I’d like to understand exactly what the problem is, and what I should do.

2

Hi @osullic,

Have you opened a Support Case? If not opened, for more information, please contact the WD Technical Support team for the best assistance and troubleshooting:

3

Not much of an answer, but here’s the explanation anyway - in case anyone else finds themselves in the same situation as I was in…

I got in touch with WD Support as suggested, and after much back and forth with the agent, there didn’t seem to be any hint as to the explanation/solution, so it seemed my only remaining option was going to be to recreate the RAID array and format the disks. But at this point, the NAS started to report that the second disk was also (suspiciously) bad. So basically, the solution in my case was to also replace the second disk. While I already had a backup in any case, I was still able to copy all the data off the NAS volume onto a portable HDD before replacing the second disk, and then I basically just started from scratch, so to speak, creating a RAID volume with two brand new disks in my enclosure.

I’m going to investigate the SMART data on the “bad” disks, and if suitable, I might resell them - with full disclosure of course.