RAID 5 rebuilding fails after replacing damaged drive

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

Hi.
My EX4100 device with four 3 TB drives in RAID 5 recently informed me of a “bad S.M.A.R.T.” problem in a drive.
I’ve replaced the bad drive with a new 4TB one and started rebuilding the RAID.
After several hours, the rebuilding failed.

I was able to recover 99% of the content (7.5 TB) by copying the files into an external device and deleted all files that gave me error while copying.
I then started the RAID rebuilding again, but it still fails when reaching 90% of the process, so I guess the error caused by the bad drive propagated into the other drives.

So my questions are:

  1. Is there a way to know what file(s) is still causing the RAID rebuilding failure?
  2. If so, should deleting the file(s) (as well as I’ve deleted all files I couldn’t copy) let the RAID rebuild correctly?

All my data come from a couple of folders, which I’ve a backup copy of, but I would like to avoid wiping the entire RAID and re-upload all 7.5 TB.

Thanks for your help.

2

if you take out the new disk you added as a replacement can you still operate in degraded mode ?
You may need to then run a off line disk diag program on that new disk.
(I still use the old WD PC diag program - that may now be EOL )

Yes it is possible to get bit rot on a raid re-build but suspect the new item first.

I use an extra fan on my nas units during a raid rebuild if the temperature looks high

For me on my PR-4100 a reload was faster than having to try 2 rebuilds.

BUT with these error you see you may need to re-test EACH disk units with a full sector by sector off line test. and was the SMART ok on the other disk units.

did you have any other red light under the other disk units come on during re-build ?

It is during a re-build of a RAID system that I wish we had error correction RAM memory.