Hello, had a question about an issue that appeared post-update that messed with my drives.


I updated my server from 7.14 to latest (7.2+) and I had an issue where 1 out of 2 SSD cache drives in my pool were unable to be mounted. The “Main” tab shows it was missing from the expected slot, and there were no options in the drop down. I shutdown and fully power cycled the server (unplugged) and then was able to select the proper drive afterwards. 



However, from that point on, I have been unable to start the Docker service and the VM service initially didn’t start, but now does libvrt or something). I have since downgraded back to 7.14 just to remove any extra variables.

Is there anything I can do to confirm what went wrong? Or even how to prevent issues like this in the future? I've had increased instability with Unraid in the past few months and I am not sure what I did to cause this one.

A running parity check shows a bunch of error corrections in syslog and filtering for docker I get messages about the Docker .img file. I suspect it's corrupted due to a drive being "missing" previously and an attempt to use it during that time (benny is my server name here):



Dec 21 22:11:46 benny emhttpd: shcmd (116): /usr/local/sbin/mount_image '/mnt/cache/system/docker/docker.img' /var/lib/docker 150


Dec 21 22:11:47 benny root: mount: /var/lib/docker: can't read superblock on /dev/loop3.


benny-diagnostics-20251221-2223.zip

Edit: Adding info asked in the Unraid discord:
After downgrading back to 7.14, VM services work again. Docker service still unable to start.
Cache pool devices (two 2tb NVME SSDs) seem to be set up in RAID1.

Edited December 22, 2025Dec 22 by Nohr
Updating with more info folks asked about on the unraid discord server.

Dec 21 18:43:13 benny kernel: BTRFS info (device nvme0n1p1): bdev /dev/nvme0n1p1 errs: wr 358871810, rd 1837035, flush 1789846, corrupt 212988, gen 0

All these errors mean one of the pool devices dropped offline in the past. Scrub the pool and post the results from the WebGUI.

Apologies! Here is an updated diagnostics set with both cache devices re-attached.

Here is what I see post-scrub:

UUID:             1f5a9131-84b9-4289-ad0f-1693109d7c6c
Scrub started:    Mon Dec 22 10:15:36 2025
Status:           finished
Duration:         0:01:26
Total to scrub:   672.99GiB
Rate:             7.83GiB/s
Error summary:    verify=23208 csum=7896581
  Corrected:      7919789
  Uncorrectable:  0
  Unverified:     0

benny-diagnostics-20251222-1018.zip

All errors were correct, which is good. Now reboot and post new diags after array start

Here is a new set:

benny-diagnostics-20251222-1132.zip

Libvirt image mounted, but it's showing some issues, if you have a backup, it may be better to restore it, if you don't, try copying everything from /etc/libvirt/qemu

Docker image is corrupt, but that one can easily be recreated

https://docs.unraid.net/unraid-os/troubleshooting/common-issues/docker-troubleshooting/#re-creating-the-docker-image-file

Then:

https://docs.unraid.net/unraid-os/troubleshooting/common-issues/docker-troubleshooting/#reinstalling-docker-applications

Also see below if you have any custom docker networks:

https://docs.unraid.net/unraid-os/troubleshooting/common-issues/docker-troubleshooting/#restoring-docker-custom-networks

Thank you very much!

I just started using VM's so I don't think I've lost much besides the configuration of a Win 11 image. I can just redo that.

For the Docker img, I will go ahead and clear it.

I also have noticed that my old Docker img file is quite large (100gb+). Is that normal behavior for 10+ containers? I have read briefly that I might be using anonymous volumes and thus they persist within that img, even when the volumes should be cleared eventually. Is there an easy way to debug that size (if it's even an issue)?

3 minutes ago, Nohr said:

also have noticed that my old Docker img file is quite large (100gb+).

It will only be that size if that is what you set under Settings->Docker. The default is 20GB which is enough for most users.

Also recommend seeing below to reset the pool errors and then keep monitoring for more:

https://forums.unraid.net/topic/46802-faq-for-unraid-v6/page/2/#findComment-700582