Trying to rebuild lost Raid5 on Thecus

I have lost a raid 5 in a 4200PRO and now I am desparatly trying to revive the Raidset.

What happened: The Raid5 over 4x 2TB WDGreen Disks degraded and I accidently marked the wrong disk as spare (this was definately my mistake, failure before always happend on drive #3, this time it was #4…), next boot the raid was gone.

[tried to fix the problem using Linux commands but to no avail].

Has anybody any experience how to get further than this?

Yes, but the success depends on what exactly was done during troubleshooting. Unless the rebuild was forced on a wrong disk order, Home NAS Recovery is a definite answer to the question.

People seem overly concerned about how to do the recovery should their NAS go down. These two cases (first, second) concern Thecus NASes.

If I create RAID 1 and the N3200Pro hw fails beyond repair (for whatever reason), can I take out one of the HDDs out and read the files on it in a Linux or Windows PC? I am only interested in reading the data once at that stage, rebuilding the RAID is a non-issue …

and

Assuming that I have a Thecus N2310. Assuming that I have a disk that *was* part of a RAID1 but the other disk is missing. What steps do I need to do with the disk and the N2310 to rebuild the RAID array and get the data off please?

I was describing this at some length in another post, but just for a short repeat, if you are worried about recovering data should the NAS dies, why not have a backup for it? The data may get damaged for reasons other than a total and utter NAS hardware failure. Lightning strike, software issue, or a number of other reasons will damage both sides of the RAID1 at the same time. RAID does not replace a backup.

Now this is complex.

I have an mdadm-created RAID5 array consisting of 4 discs. One of the discs was dropping out, so I decided to replace it. Somehow, this went terribly wrong and I foolishly succeeded in marking two of the (wrong) drives as faulty, and then re-adding them as spare.

Now the array is (logically) no longer able to start:

mdadm: Not enough devices to start the array.

Degraded and can’t create RAID,auto stop RAID [md1]

…

As I don’t want to ruin the maybe small chance I have left to rescue my data…

This sure is complicated. Obviously, if you fail two array members, RAID5 goes down. Worse yet, once this happens, it stays down. You can’t tell it to accept the spares back in a normal way. Theoretically, some more fiddling with mdadm can force the array back into shape, but I doubt it is safe given a DIY environment. If your unit is still under warranty (this particular case was with Thecus), then by all means open a ticket and ask them to fix the issue – they are pretty good with mdadm. If the case is beyond Linux repair, fall back on our Home NAS Recovery – we are pretty good too.