Had half my cache pool go dark last week when my nvme drive failed, leaving me with only one. Unfortunately, I decided to play it cheap and wait a week for a replacement to come in and now my other cache drive is listed as unmountable.

Tried stopping, removing, restarting, adding and stopping and restarting the array, to no avail. Diagnostics attached below if anyone has any suggestions. Looks like there were some SMART errors on the drive but it passed the self-test.

labs-unraid-diagnostics-20260326-1304.zip

Please post the ouput from btrfs fi show

root@labs-unraid:~# btrfs fi show

Label: none uuid: 13a2c81e-5a2c-4547-abf7-dd82406e360c

Total devices 2 FS bytes used 254.13GiB

devid 1 size 476.94GiB used 324.03GiB path /dev/nvme0n1p1

devid 2 size 476.94GiB used 324.03GiB path /dev/sdb1

Label: none uuid: 6a1fa145-e043-4f9d-87cb-8b24b473d52e

Total devices 1 FS bytes used 372.00KiB

devid 1 size 80.00GiB used 2.02GiB path /dev/loop2

Label: none uuid: 0c5702a5-7d58-42ee-acb3-1e311dd15d13

Total devices 1 FS bytes used 416.00KiB

devid 1 size 1.00GiB used 126.38MiB path /dev/loop3

root@labs-unraid:~# btrfs fi show

Label: none uuid: 13a2c81e-5a2c-4547-abf7-dd82406e360c

Total devices 2 FS bytes used 254.13GiB

devid 1 size 476.94GiB used 324.03GiB path /dev/nvme0n1p1

devid 2 size 476.94GiB used 324.03GiB path /dev/sdb1

Label: none uuid: 6a1fa145-e043-4f9d-87cb-8b24b473d52e

Total devices 1 FS bytes used 372.00KiB

devid 1 size 80.00GiB used 2.02GiB path /dev/loop2

Label: none uuid: 0c5702a5-7d58-42ee-acb3-1e311dd15d13

Total devices 1 FS bytes used 416.00KiB

devid 1 size 1.00GiB used 126.38MiB path /dev/loop3

root@labs-unraid:~#

31 minutes ago, cybergguy said:

Total devices 2 FS bytes used 254.13GiB

devid 1 size 476.94GiB used 324.03GiB path /dev/nvme0n1p1

devid 2 size 476.94GiB used 324.03GiB path /dev/sdb1

The pool currently consists of two devices

First, unmount the NVMe device from UD

/dev/nvme0n1p1 477G 255G 222G 54% /mnt/disks/P210EDCB23101904817

Then on main click on the first device for that pool and then "remove pool"

back on main, create a new pool with the same name and 2 slots

assign both pool devices, leave the filesystem set to auto

start the array to import the pool

Thanks Jorge - before I give that a shot, that second device (the nvme drive) was the one that had failed. The system refused to recognize the drive at all, other than at the BIOS level. I had been operating on solely the other device for a couple of weeks until I got this error, and now Unraid sees the nvme drive again.

Is there any concern that the two are out of sync? Will re-adding that nvme device cause any harm?

Thanks for your assistance!

If it's a mirror, Btrfs will know if one is out of sync, but you can also disconnect that drive and mount the pool with just the other one. What you cannot do is try to mount with just one while having the other connected and unassigned. Also, the NVMe device most likely just dropped offline, not failed.

8 hours ago, JorgeB said:

If it's a mirror, Btrfs will know if one is out of sync, but you can also disconnect that drive and mount the pool with just the other one. What you cannot do is try to mount with just one while having the other connected and unassigned. Also, the NVMe device most likely just dropped offline, not failed.

Thanks - gave it a shot, this time the pool started but it doesn't seem to be reading the drive it had previously labeled as unmountable. Docker and VMs are both unable to start because of file system errors it seems.

I've attached diagnostics, not sure what my next step would be. It does seem like both of the cache drives have issues. Not sure if there's any way to safely back up what's in cache at this point and start with at least one new drive.

labs-unraid-diagnostics-20260328-1206.zip

Scrub the pool and post the results.

Also, the Docker image should 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

Thanks for the links and direction Jorge, that did the trick! Scrubbed, then went through and deleted the Docker image and recreated it, completely back up and running now thanks for your help!