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Cache Drive Unmountable after Docker vDisk Removal

Featured Replies

Looking for some guidance on next steps. I was having a bunch of docker issues on my system. Randomly stopping, not starting, certain containers acting flaky. In any case, I decided to delete the vDisk and after reboot my cache pool turned up with an "unmountable" message. I am hoping someone can point me in the next best course of steps. i have attached Diagnostics below. Thanks in advance for some guidance here. Sorry if this is in the wrong bucket.

tower-diagnostics-20250727-1735.zip

Solved by JorgeB

  • Community Expert

Post new diags after array start please.

  • Author

Currently my cache is unmounable, preventing me from starting the array again. I would love to recover my cache pool, but everthing I try is not an acceptable move in unraid. If I remove the cache pool, would I be able to add a fresh pool and copy the date from the old drives, or is this process a one way data loss? At this point, it looks like I need to rectify my cache pool issue before I will be able re-start my array. Thanks again for any guidance you may be able to provide.

  • Community Expert
27 minutes ago, drewd said:

Currently my cache is unmounable, preventing me from starting the array again.

Unmountable cache does not prevent array start, it will just not mount, unless there's another issue. Do you get an error when trying to start the array?

  • Author

I tried to unsuccessfully add a drive to the pool hoping to recover the pool. I am now faced with Wrong Pool State - cache invalid expansion

  • Community Expert

That's a different issue, post the output from btrfs fi show

  • Author

Label: none uuid: a16da88c-8713-48b8-bdee-62a4c9889dde

Total devices 2 FS bytes used 226.82GiB

devid 1 size 465.76GiB used 464.74GiB path /dev/sdac1

devid 2 size 465.76GiB used 464.74GiB path /dev/sdab1

Label: none uuid: 0c1f9f61-8156-42b2-a727-7bec90ac7ffc

Total devices 1 FS bytes used 3.59TiB

devid 1 size 3.64TiB used 3.64TiB path /dev/sdo1

Label: none uuid: ff935007-27b4-4f7d-bd4a-a10f51378c2e

Total devices 1 FS bytes used 4.91TiB

devid 1 size 5.46TiB used 5.30TiB path /dev/sdm1

Label: none uuid: 78c765d7-2deb-4b38-9c10-38aab5010095

Total devices 1 FS bytes used 3.63TiB

devid 1 size 3.64TiB used 3.64TiB path /dev/sdu1

Label: none uuid: c88e45ff-c3d4-4f09-bc8d-4bdf278276e5

Total devices 1 FS bytes used 3.54TiB

devid 1 size 3.64TiB used 3.63TiB path /dev/sdb1

Label: none uuid: 1b9ebae0-3615-46ce-bfdc-8a270627d8e0

Total devices 1 FS bytes used 3.55TiB

devid 1 size 3.64TiB used 3.63TiB path /dev/sdi1

Label: none uuid: 116771a4-95d5-4652-bd70-5c0cc91a1ed2

Total devices 1 FS bytes used 4.65TiB

devid 1 size 5.46TiB used 5.32TiB path /dev/sdn1

Label: none uuid: 34cb677f-7eca-402f-84cb-83f1f5ce62f6

Total devices 1 FS bytes used 3.58TiB

devid 1 size 3.64TiB used 3.62TiB path /dev/sdv1

Label: none uuid: 12d032f0-1aa2-46a3-803f-d03eeb92ef01

Total devices 1 FS bytes used 3.61TiB

devid 1 size 3.64TiB used 3.62TiB path /dev/sdc1

Label: none uuid: b199aedb-7759-4e01-8636-ceaa7d9046e4

Total devices 1 FS bytes used 4.73TiB

devid 1 size 5.46TiB used 5.28TiB path /dev/sdt1

Label: none uuid: 79583828-3bbe-47ca-a853-8d1d615bbc8f

Total devices 1 FS bytes used 2.71TiB

devid 1 size 2.73TiB used 2.73TiB path /dev/sdj1

Label: none uuid: e31dc21e-2eaf-4ed2-b01f-53fc666ab0f4

Total devices 1 FS bytes used 3.66TiB

devid 1 size 5.46TiB used 4.47TiB path /dev/sdh1

Label: none uuid: e0463d61-dda3-473c-a877-dd088873bc3b

Total devices 1 FS bytes used 3.62TiB

devid 1 size 3.64TiB used 3.64TiB path /dev/sdp1

  • Community Expert
3 hours ago, drewd said:

Total devices 2 FS bytes used 226.82GiB

devid 1 size 465.76GiB used 464.74GiB path /dev/sdac1

devid 2 size 465.76GiB used 464.74GiB path /dev/sdab1

I assume this is the pool, if yes:

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 2 slots

assign the pool devices, leave the filesystem set to auto

start the array to import the pool

Then post new diags to see why it's not mounting.

  • Author

may be a silly question - do i remove the drives from the pool first before removal - of that doesnt matter. thanks again!!

  • Community Expert
  • Solution

Both metadata copies are corrupt:

Jul 28 14:30:42 tower kernel: BTRFS error (device sdac1): incorrect extent count for 5018849968128; counted 1341, expected 1338

Jul 28 14:31:08 tower kernel: BTRFS error (device sdac1): incorrect extent count for 5018849968128; counted 1340, expected 1337

See if it mounts read-only:

https://forums.unraid.net/topic/46802-faq-for-unraid-v6/page/2/#findComment-543490

  • Author

Thanks so much for all the help with this. I was able to mount the cache pool into a created /temp folder with mount rescue command. After a couple of failed attempts - it finally mounted into my temp dir. I am copying the data into the array as i type this.

Making some assumptions here on process forward.
1) After copy off old cache into array, I can remove pool in the system
2) then stop array, remove drives
3) replace drives
4) Start array, create new pool and add drives then
5) copy data back from array to new cache pool

That sound about right?

  • Community Expert

After copying the data, you can just reformat the pool, no need to remove the devices.

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