RAID 5 reconstruction


One example how thing can go wrong very quickly
I have a EX4100 with 4 x 1TB WD RED in Raid 5, latest firmware
I’ve decided to upgrade to 4 x 4TB WD RED still in Raid 5
I removed drive number 4, and replaced with a 4TB one
I went to the browser to access the NAS webpage, and started the RAID rebuild
Drive tested OK, and started the rebuild, and at some percentage… trouble begins…
Rebuild process stops because drive nº2 fails…
I rebooted the NAS, and drive nº 2 still show as “BAD”
And now get’s worse…
Turned off the NAS, removed all drives to clean dust and to copy the serials
Plug the drives again at the same position, and at the nº4 bay I put the “old” 1TB drive, and turn on the NAS
And now all 4 drives appear as “GOOD”, but I have no RAID configuration at all at web the NAS web interface

Can something be done to recover this ?

What happens if you put that 4TB drive back in slot 4?

Unfortunately I had to assume the loss of data
It was not total loss, because I have backups…
I needed to put the NAS up again, so I’m not able to make tests any more…

Thanks for all that read this post
Thanks NAS_User

I have found in these situations that data is often recoverable. . . “but one wrong move” and it all goes poof.

Here, I “suspect” when you put in the 4TB drive in the box; the system began to rebuild the raid. This rendered the old 1TB disk as “obsolete” and not recognized as part of the array.

But I am only speculating. . . I know nothing.
I am not sure what happens if you hibernate the system during a rebuild (or worse. . .if you just pull the plug)