I have 2 failed drives (disk 1 and 4) at the same time in a dual-parity setup. My current parity was 18TB each. I bought 2 new 20TB drives. Put one in and after preclear, I assigned the new one in one of the parity spots and the old 18TB parity as a data disk 1 (one of the failed spots). Both of them shows a blue square and unraid let me do the parity upgrade. That took 2 days straight.

It just complete and it wanted to start the array to do a data rebuild on one of the failed drives, but I wanted to start the rebuild on the drive that only had a few TBs used on it. So in the GUI I assigned the old 18TB drive to disk 4 and GUI wouldn't let me start it. So I assigned it back to the disk 1 spot but now it won't let me do anything again except it wants to start the parity upgrade all over again!!

Nothing changed except assigning that old disk from 1 to 4 and back, I never touched the parity assignments at all and I don't want to start the same 2-day copy over again! Is this a bug that it thinks the parity is no longer good? I'm not sure what to do to avoid it starting the same exact parity upgrade process again? (I'm on v7.1.4)

Edited August 4, 2025Aug 4 by djvj
adding version

You cannot upgrade parity with a disabled disk; please post the diagnostics.

According to the docs, they have an example that sounds exactly like this:
https://docs.unraid.net/unraid-os/manual/storage-management/#upgrading-parity-disks

Parity Swap

This is a special case of replacing a disabled drive where the replacement drive is larger than your current parity drive. This procedure applies to both the parity1 and the parity2 drives. If you have dual parity then it can be used on both simultaneously to replace 2 disabled data drives with the 2 old parity drives.

NOTE: It is not recommended that you use this procedure for upgrading the size of both a parity drive and a data drive as the array will be offline during the parity copy part of the operation. In such a case it is normally better to first upgrade the parity drive and then afterward upgrade the data drive using the drive replacement procedure. This takes longer but the array remains available for use throughout the process, and in addition, if anything goes wrong you have the just removed drive available intact for recovery purposes

Why would you want to do this? To replace a data drive with a larger one, that is even larger than the Parity drive.

Unraid does not require a replacement drive to be the same size as the drive being replaced. The replacement drive CANNOT be smaller than the old drive, but it CAN be larger, much larger in fact. If the replacement drive is the same size or larger, UP TO the same size as the smallest parity drive, then there the simple procedure above can be used. If the replacement drive is LARGER than the Parity drive, then a special two-step procedure is required as described here. It works in two phases: - The larger-than-existing-parity drive is first upgraded to become the new the parity drive - The old parity drive replaces the old data drive and the data of the failed drive is rebuilt onto it.

As an example, you have a 1TB data drive that you want to replace (the reason does not matter). You have a 2TB parity drive. You buy a 4TB drive as a replacement. The 'Parity Swap' procedure will copy the parity info from the current 2TB parity drive to the 4TB drive, zero the rest, make it the new parity drive, then use the old 2TB parity drive to replace the 1TB data drive. Now you can do as you wish with the removed 1TB drive.

I let it copy the parity to the drive a 2nd time and it did the same thing. It finished and got a log entry disk4 would be reconstructed and I don't see anything happening on the server and looks to be in the same state as before:

3 minutes ago, djvj said:

According to the docs, they have an example that sounds exactly like this:

Yes, sorry, I misread this post.

Parity swap cannot be interrupted; if you change something you would need to start over.

If you are sure the copy was correct, you could have done a new config to force the rebuild, but since you did the copy again, just start the rebuild , without touching anything else.

I can't start it though as these are my options. Note, I did not reboot or power cycle the server.

Forgot to attach the diagnostics, sorry storinator-diagnostics-20250806-1347.zip

4 minutes ago, djvj said:

Note, I did not reboot or power cycle the server.

Did you change any assignments? You cannot change anything after the parity copy completes; there should have been an option to start the rebuild, it won't start by itself.

After the parity copy complete, the array status should look like this:

And the star button should be enabled for the rebuild:

I did change before I started. However, I just woke up and refreshed the page, so no I did not change anything since this last try.

I think the only option now is to start again for a 3rd try? Maybe I should reboot first in case there is some bug going on?

13 hours ago, djvj said:

Maybe I should reboot first in case there is some bug going on?

Should not be needed, but it won't hurt.

So for the 3rd time, I rebooted and it did give me the start option after the parity-upgrade! So it's rebuilding now finally. Thanks for your help.

Edited August 8, 2025Aug 8 by djvj

So what I was most afraid of happening has just occurred. During the rebuild, another disk just started dumping errors! Now I'm afraid of what to do as the rebuild is only 20% in?

Post new diags please.

storinator-diagnostics-20250809-1004.zip
Here you go

SMART for disk2 looks fine; looks more like a power/connection issue, and before those errors disk4 had already dropped offline, again looks like a power/connection issue. Are using any power splitters?

In any case, check/replace cables for those disks, remove any power splitters that are spçlititng a SATA port to more than 2, then try rebuilding again.

Yes it uses splitters. I'll check those then and see if it comes back up. Thank you