Hi all, not even sure how possible this is, but certainly hope that it will be!

I have a 2 drive array with single parity, and today both of my array drives failed due to a PSU issue. I realize that under normal circumstances I would be screwed, but my second array drive has about 26mb of data on it and the rest is zeroed, so if I'm not mistaken, it should be possible to recover drive 1 in its near entirety. I definitely don't want to walk into this blind, though, so any recommendations or help would be appreciated.

You can't rebuild 2 disks with single parity. Parity doesn't know anything about the files,it is all just bits for rebuild.

Probably the way forward is New Config.

In what way did the disks fail?

Attach Diagnostics ZIP to your NEXT post in this thread.

Just now, trurl said:

In what way did the disks fail?

Magic smoke, a faulty rail. The data might be recoverable by a specialist, but no hardware I have can even recognize that a drive is connected. They have that fresh, fried component smell.

With New Config, can I assert that the new zeroed drives both have valid parity, and then somehow error Drive 1 and cause a rebuild on it? Ideally if I pretend that the second drive never existed, or zero a new drive and posit it as Drive 2, it should only corrupt about 30mb of data on the drive I care about.

Diagnostics attached.

tower-diagnostics-20251128-1644.zip

Edited November 28, 2025Nov 28 by bongounicorns

59 minutes ago, bongounicorns said:

Magic smoke

Did you try to reuse a modular cable from a different PSU? There is no standard pinout for modular PSUs and frying drives is a common outcome when using incompatible modular cables.

Often the data on the drives will still be OK if you can just replace the circuit board on the drive with an identical model.

1 hour ago, bongounicorns said:

With New Config, can I assert that the new zeroed drives both have valid parity, and then somehow error Drive 1 and cause a rebuild on it?

Unlikely parity can emulate disk 1 without disk 2, regardless of how much space was used on drive 2.

I guess you could try it and maybe check filesystem could allow emulated disk1 to be mounted.

No point in having disk2 in the New Config since it won't contribute anything to parity calculation if it is zeroed.

1. New Config, the only thing you might retain is parity so that really won't matter. Then Apply.

2. Assign parity to parity slot and new disk as disk1.

3. Check BOTH Parity Valid and Maintenance mode checkboxes, then start the array.

4. Stop the array, unassign disk1, start the array in Normal mode. This will emulate disk1 from parity. Probably it won't be mountable without further work.

Then post new diagnostics.

@trurl Sorry for the delay, Black Friday shipping made my new drive take a bit to come in.

Here are the new diagnostics. You are correct that it currently shows as unmountable when running off of parity alone trying to emulate Disk 1.

Appreciate the help so far.
tower-diagnostics-20251203-1155.zip

Edited December 3, 2025Dec 3 by bongounicorns

No filesystem signature is being detected on the emulated disk1, do you know what filesystem was being used?

Also post the output from wipefs /dev/md1p1 with the array started, and despite the name, that as written won't wipe anything.

@JorgeB
It was XFS.

How do I tell if it's attempting to emulate disk1? It does give me a "Unmountable: unsupported or no filesystem" message on Disk1's line, and it's set as Not Installed currently. Running that command produced no output, btw.

Edited December 3, 2025Dec 3 by bongounicorns

7 minutes ago, bongounicorns said:

Running that command produced no output, btw.

That's expected; it was just to confirm.

You can try to check filesystem on it, to see if xfs_repair can recover from a backup superblock. With the array still started, type

xfs_repair -v /dev/md1p1

@JorgeB No valid secondary superblock. Am I screwed?

Edited December 3, 2025Dec 3 by bongounicorns

Possibly, that suggests the missing disk wasn't as clear as you thought, so parity is very far from valid without it.

You can try rebuilding to a new device, then run UFS Explorer on it, the free trial should show if it can recover any data.

I used a free data recovery tool on a rebuilt drive and was able to get what I needed from it. Thanks so much for the help with this! Lesson learned to make more frequent backups.