I've had a few issues with my unraid server over the last few days.
It ran a normal pairity drive (it was 8TB) check on the 1st of the month, as it does every month. That came back with zero errors. But almost immediately afterwards, the parity drive was marked "disabled" with a red cross, and parity protection was gone.
Hmm.
I followed instructions to stop the array, remove, start, re-add the parity drive, start. This didn't work, the drive remained disabled. I assumed there was a faulty drive, and ordered a replacement disk. I figured i'd use this time to increase the size of the parity disk, so I ordered a 16tb drive. When that arrived, I put it into the array, and was still having the same problem.
In the end after much trial and error, I think the SATA cable was at fault, somehow just reversing it fixed the problem. The new parity drive was picked up and sync restarted without issue.
But! It was syncing really slowly. It's been running at only 25mb/sec overnight. See pic 1.
I came to post here, so I ran diagnostics export (attached).
Then i re-checked the sync status and it's now running at ~200mb/sec. See pic 2. Ok.. good. but why was it slow before?

Any ideas what's going on?
Thanks!

server-diagnostics-20240705-0827.zip

The only obvious thing I can think of was when it was running slow there was reading/writing going to some other disk in the array.   This would dramatically slow down the parity sync speed until it completed.

Ok thank you. But I am not sure that'd be the issue. If anything, overnight it would get less use I would have thought.

 

I'll keep an eye on it I guess