37 minutes ago, Tyrus said:

My old array was sdc as data and sdb as parity

39 minutes ago, Tyrus said:

looks like I killed all the data on (sdb)

Possibly the sd identifiers changed during all this. That often happens when disk connections are changed. That is why we usually don't talk about those identifiers. It always makes more sense to give some of the serial, usually the last 4 characters is enough, when discussing specific disks.

But, assuming the sd identifiers didn't change, and sdb was the old parity, then it didn't have any data to kill.

43 minutes ago, Tyrus said:

used the old parity(sdb) as an additional data disc on the array.

Do you mean you assigned the old parity to a new slot that didn't already have a data disk assigned to it? Or did you use the old parity to replace a disk (that is what would usually be meant by parity swap).

Sorry, missed the answer on the new page.

So to clarify it with Serials:

My original array was (WS255S39) as data and (WS255SBX) as parity.

I wanted to swap the WS255SBX(old parity) with a new 8tb drive as the new parity and use the now free WS255SBX(old parity) as a second data drive beside WS255S39(old data drive) to expand the storage. Since my old data drive was full.

So the new config looked like that:
WS255S39(old data) + WS255SBX(old parity, now new data after parity swap) and WRQ31N7K as the new parity.

The array was working like expected and I could copy new data to the array, since it was expanded by WS255SBX. The only problem was, that I was getting a ton of parity errors.

After some time I tried to fix the parity errors with the "write corrections to parity disc" command and somewhere after that and the upgrade to 7.2.2 the data on WS255SBX was gone.

I hope that helps :)

unraidnas-diagnostics-20260106-2214.zip

Edited January 6Jan 6 by Tyrus

9 minutes ago, Tyrus said:

the "new" second data disc

Was the mountable unassigned disk originally assigned to that slot?

Is sdb supposed to be disk1?

Or is sdc supposed to be disk1?

And were you adding a data disk or replacing a data disk?

On 1/5/2026 at 3:20 PM, Tyrus said:

Could it be that by fixing the parity problems, the drive was put back in the pre-cleared state

No, parity correction only writes to parity

sdc is disc 1(5S39)
sdb is disc 2 (5SBX)

Just now, trurl said:

No, parity correction only writes to parity

Yeah, that is what i thought too but that's all I have done beside upgrading to new Unraid version after that. I haven't done any changes/configs or whatever besides that. And then suddenly disc 2 was showing as "unmountable" etc.

Edited January 6Jan 6 by Tyrus

Before all this, you only had parity and disk1.

Correct?

Just now, trurl said:

Before all this, you only had parity and disk1.

Correct?

yes

After adding disk2, you think you had written some data to disk2.

Correct?

Yes, I have definitly written data to it, since disk 1 was full and I was getting errors that there was no space, before adding disc 2. And the data was showing up(I think)

If disk2 was disabled/emulated, you could still write data to it.

But, you wouldn't be able to correct single parity with a disabled data disk.

I asked earlier if you did parity swap. Did you read the link about parity swap? Parity swap is only used to replace a disk. But it seems like you were adding a disk instead. And the link you gave was for replacing a disk and doesn't discuss adding a disk at all.

Did you actually follow any of the instructions for parity swap?

As far as I can tell, there was no emulation message.

I was replacing the parity disc. Isn't parity swap exactly for that? I replaced the old parity disc with a bigger one. After the replacement I used the now unused old parity disc as a second data disc to increase the size of my data-array.

Edited January 6Jan 6 by Tyrus

Parity swap replaces parity with a larger disk and uses the old parity to replace a data disk. You should read about it for a more complete explanation.

Parity swap is not needed if you are just replacing parity. Then you can add the old parity to a new slot if you want.

If you add a disk to a new slot in an array that already has valid parity, Unraid would clear it if it hadn't been precleared, so parity would remain valid. A clear disk is all zeros so has no effect on parity.

But, after adding the disk to a new slot, you would have to format it before you could use it because a clear disk doesn't have any filesystem and format creates an empty filesystem on the disk.

I'm explaining all this because your explanation seems to be missing some important information, and I'm trying to fill in the gaps.

18 minutes ago, trurl said:

Did you actually follow any of the instructions for parity swap?

If you did, then at some point you must have not completed it since you didn't replace a disk.

1 minute ago, trurl said:

since you didn't replace a disk.

didn't replace a data disk

Oh, so I misunderstood parity swap and wasn't reading it thoroughly enough. Is this the probable cause for the data loss? Since it was in november I won't be able to recall all the steps I did.

I think I misunderstood replace the data disk with put the old parity as new data disk.
I think the only difference is, that I placed the old parity drive in a new slot, instead of replacing an existing data-slot with the old parity drive. Like it is said in the instruction(step 12)

Edited January 6Jan 6 by Tyrus

If you added a precleared disk to a new slot but didn't format it, it would be unmountable and still have the preclear signature. And it would stay like that until you did format it. But you wouldn't be able to write to it.

Are you sure you weren't writing to cache instead?

I must have formatted it at some point. But I can't say it for sure.

I am not even sure my cache is configured correctly. That is something I was planing to tackle later and make a proper config. Because I have questions about it. Since 500GB and 1TB Cache drives only show up as 756GB in total.

5 minutes ago, Tyrus said:

I think the only difference is, that I placed the old parity drive in a new slot, instead of replacing an existing data-slot with the old parity drive.

Not sure if Unraid would let you add a disk during the parity swap procedure. It would be technically possible (but not recommended) to allow that if it then cleared the disk, or if the disk was precleared. But if you put old parity in the new slot, it wouldn't be a clear disk.

I know I have done something to the old parity. But I can't remember if it was pre-clearing or formating.
But when I finshed the procedure there were no warning or problems. Except the parity errors that appeared durung the next parity check.

Edited January 6Jan 6 by Tyrus

Just now, Tyrus said:

500GB and 1TB Cache drives only show up as 756GB in total.

Actually that is even wrong. Default is raid1 mirror so total capacity is the smaller of the 2 drives.

Doesn't seem like we can make any progress on this even if you had perfect memory.

How important is the data (you think?) you are missing.

And a more general question. Do you have good (enough) backups? Parity is not a substitute for backups. Plenty of much more common ways to lose data besides a failed disk, including user error. If you accidentally delete something, for example, parity will agree it has been deleted.