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Cache pool BTRFS missing device(s). unable to start pool rebuild

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Yesterday, one of the SSDs in my pool of 2 SSDs failed, leaving me with a dead drive. I replaced it with a new SSD of the same size. However, despite the replacement, BTRFS isn't initiating the repair for the RAID on this pool. Additionally, I'm receiving emails indicating that the second SSD in the pool is 'missing' only when the array is stopped.

 

While I can restart the array, whenever I attempt to move the Vdisk to the array to replace the other SSD, the transfer speed drops drastically to 2-5Mb/s with an estimated time of 1600 hours, as the Vdisk image is 2TB.

 

For troubleshooting so far I have:

Tried different cables and ports on my Motherboard

Tried rebooting the Server

Tried using file explore to move the vdisk

tried using Cli to copy the vdisk

 

All attempts to move the data to the array temporarily start at normal speeds then after about a minute drop to 2-5Mbs

 

 

It's worth noting that when I check the status using 'btrfs replace status /mnt/pool_name', it shows 'never started' for the pool in question.

 

Any thoughts or advice on resolving this issue would be greatly appreciated. I'm concerned about the data on this Vdisk and want to ensure it's not lost. Thank you."

tower-diagnostics-20240204-1624.zip

  • Community Expert

Post the output of 

btrfs fi show

 

  • Author
3 hours ago, JorgeB said:

Post the output of 

Output of Command: 

 

Label: none  uuid: e03c4769-3927-4173-8e19-cac6dcb664a4
        Total devices 4 FS bytes used 1.32TiB
        devid    3 size 0 used 0 path  MISSING
        devid    4 size 1.82TiB used 905.03GiB path /dev/sdc1
        devid    5 size 1.82TiB used 760.00GiB path /dev/sdb1
        devid    6 size 1.82TiB used 450.00GiB path /dev/sdd1

  • Community Expert

Reboot to clear the logs, start the array with the pool as is currently and post new diags after 5 minutes

  • Author

Was getting normal ish speeds on the Pool for a while after the reboot but it is stuck at about 655Kbs currently. Attached logs from when I noticed the speeds drop.

tower-diagnostics-20240205-1619.zip

  • Community Expert

There are what look like power/connection issues with the PNY pool device, replace cables and try again.

  • Author

I swapped the SATA power cable and connected the drive to a different SATA port with a new cable and restarted Unraid 

 

tower-diagnostics-20240206-0636.zip

  • Community Expert

No errors so far, lets see if the missing device can be deleted now.

  • Author

I ran "btrfs fi show" again, here is the result. 

 

Label: none  uuid: e03c4769-3927-4173-8e19-cac6dcb664a4
        Total devices 4 FS bytes used 1.32TiB
        devid    3 size 0 used 0 path  MISSING
        devid    4 size 0 used 0 path /dev/sdaa1 MISSING
        devid    5 size 1.82TiB used 833.00GiB path /dev/sdb1
        devid    6 size 1.82TiB used 649.00GiB path /dev/sdc1

 

I also noticed that the 2TB PNY is now showing in the pool and under unassigned devices?

 

348911902_Screenshot2024-02-06at7_17_31AM.thumb.png.ee4a3e4b6563ac8e3de245cbd219a0ec.png

 

653905034_Screenshot2024-02-06at7_17_41AM.thumb.png.9906453a99017ce3cdd96a4bc8420120.png

 

Disk Log for the 2TB PNY 

 

777331224_Screenshot2024-02-06at7_18_10AM.thumb.png.b899286a00d690faf71f17b1f299c871.png

 

 

  • Community Expert

If the device still has issues with new cables it may be a device problem.

  • Author

Rebooted and it cleared up the duplicated devices, the BTRFS Pool is doing something. pretty sure that PNY SSD is in the processes of dying... thought it was strange they both decided to bite the bullet at the same time. 

 

Is there a way to check what operation is being run on the pool? or to stop it? 

 

Tried to run "btrfs dev del missing /mnt/plexmeta" 
ERROR: unable to start device remove, another exclusive operation 'device remove' in progress

 

 

Screenshot 2024-02-06 at 9.04.04 AM.png

  • Community Expert
Just now, Stanui said:

ERROR: unable to start device remove, another exclusive operation 'device remove' in progress

Unraid starts removing the device automatically after array start, and AFAIK it's not possible to cancel that, possibly you can try mounting the pool read only and try copying what you can.

  • Author

Gave that a try, it's running but at 1.45-1.56MB/s with an ETA of 13 days. Let the transfer run to see if it errors out?

 

I was using the pool for a Vdisk and cant really grab one file vs the entire Vdisk image. 

  • Community Expert

Is that with pool mounted read only or while still also removing the missing device?

  • Author

With the Array started normally I followed the Mounting pool read only instructions to mount it to the temp directory. 

 

Unraid is still showing a BTRFS operation is running 

  • Community Expert
50 minutes ago, Stanui said:

Unraid is still showing a BTRFS operation is running 

OK, I wasn't sure if it would continue with the pool in read-only mode.

  • Author

Gotcha, Logs show the Pool is doing the following 

 

Feb  6 10:56:33 Tower kernel: BTRFS info (device sdz1): found 4784 extents, stage: update data pointers
Feb  6 10:57:00 Tower kernel: BTRFS info (device sdz1): relocating block group 2025308815360 flags data|raid1

 

Im assuming it's trying to rebuild since the original 2nd drive died? but not sure if its actually making progress.

  • Community Expert

It's doing a balance, this is normal, and as long as new similar lines keep appearing it's making progress.

  • Author

Alright thanks, I'll just let it be for now. 

 

Thanks for the help. 

  • 2 weeks later...
  • Author

To close this out if anyone finds it in the future. 
 

I ended up pulling both the PNY SSDs from the cache pool as they were completely dead and were not even being recognized anymore.

 

Unfortunately lost the Vdisk on the pool. I configured the pool with some new WD Blue SSDs. 
 

TLDR: drives were dead and the rebuild time went from 6 weeks to 3 months and I said forget it. 

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