My storage array had one drive that was offline and being emulated for too many SMART errors and needed replacing. I moved a healthy 14tb parity disk into its place and upgraded the parity slot to a 24tb disk per the parity swap instructions (or so I thought, more on that in a moment). I have a few more 24tb disks with the intention of getting both parity drives and a few data drives updated in the span of a few operations.

I got through step 14 in that doc, where I copied parity but now I am not seeing a way to start the array back up:

I thought at first that maybe some other operation is happening post-copy but no disks show any read/write traffic on the Main screen and it remained like that for 5-6 hours yesterday after the copy finished. I tried checking the box and running it again to no avail. I've also rebooted the server without any change.

Someone on reddit pointed out that I should not have modified both disks at the same time. The good news is that I am using two parity disks so I don't think anything is lost yet but I need to be very careful at this point trying to unwind this mess. If I can provide any other info to inform a solution please let me know and I will respond quickly with anything needed. Rookie mistake, I know, but hopefully there is a way to get this thing back on track.

8 minutes ago, hunsbct said:

Someone on reddit pointed out that I should not have modified both disks at the same time.

Your description doesn't sound like you changed anything except the drives involved in the parity swap. Can you clarify?

9 minutes ago, hunsbct said:

also rebooted the server

I don't suppose you happened to get diagnostics before the reboot?

In any case,

Attach Diagnostics ZIP to your NEXT post in this thread.

12 minutes ago, hunsbct said:

moved a healthy 14tb parity disk into its place and upgraded the parity slot to a 24tb disk per the parity swap instructions

OK, I get it. So the original parity disk wasn't present then? Where did you think it was going to copy parity from?

Attached are the current diagnostics. Unfortunately I did not capture them before the upgrade so again, lesson learned for next time.

Your description doesn't sound like you changed anything except the drives involved in the parity swap. Can you clarify?

Essentially, instead of only removing the old parity drive and replacing it with a new one, I moved the old parity drive to a data drive slot and added a new disk as the replacement parity disk.

I thought it would be copying parity from the second parity disk.

diagnostics-20251009-0903.zip

May be worth clarifying that since there is dual parity I thought it was safe to move both drives. My current thinking is maybe I can emulate the data disk and just focus on getting parity back, then rebuilding the data disk in a secondary step? But obviously I'm deferring to the experts on this one.

Edited October 9, 2025Oct 9 by hunsbct

Parity2 isn't the same as parity1, it is a different algorithm with different results. Otherwise it wouldn't be able to provide any more information than parity1 and so couldn't rebuild 2 disabled disks. So, parity2 is not involved in the copy. Copy must come from the original parity disk.

In any case, since you had dual parity, parity swap wasn't necessary. Parity2 will allow you to rebuild the data disk, and parity1 will be rebuilt from all assigned data disks (emulated data disk is used instead of the disabled/rebuilding data disk).

The real question before proceeding is whether or not the disabled/emulated data disk is mountable.

See if you can unassign both new parity1 and the new data disk, start the array, and post new diagnostics.

When I unassign both of those disks, I see a warning that the array is missing a disk which makes sense:

I was able to start the array and generate the attached diagnostics

diagnostics-20251009-0922.zip

Missing disk10 is being emulated just fine by parity2. It shows 21% usage. You should be able to browse its files if you want to take a look.

The drive assigned as disk10 in your screenshot, and in those other diagnostics you posted, has some SMART errors. And those are showing up in syslog as a drive problem. So I wouldn't use that for the rebuild.

Is that the original disk10? Or is it the original parity1? Or is it a new disk?

Disk 10 in this case is the former Parity 1 disk. It is slated for immediate replacement anyway so I can remove it and replace with a new disk for the rebuild.

You're thinking I rebuild that first and then add back the new 24T disk as parity 1 once I have a full data array correct?

Do you already have a new disk10 ready to go? If so, you can rebuild both at the same time.

Yes, I have a few new drives such that I could do both simultaneously if that is safe and feasible. More than happy to take it one step at a time if that has any meaningful advantages.

Remove that bad disk and plug in a new disk in its place, at least as large as original disk10 but no larger than parity2.

Then, without assigning parity1 or new disk10, start the array and post new diagnostics. That will allow us to check out the new disk and also see if the connections are OK.

Will do. I'll be able to stop by and do that in a few hours and I'll report back. Can't thank you enough for your help so far, really appreciate you taking the time.