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Cache Pool shows "unmountable - unsupported or no file system"

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Hello, I realized several Docker services were down, and was surprised to see the Docker service had failed. Then looking at the array status, the cache pool of 2 SATA ssd's (BTRFS in raid 1) shows as "unmountable." I noticed several other issues on this forum with the same issue recently but am concerned about deleting data.

image.png

 

What I've done so far:

Stopped the array, removed the cache drives by setting pool slots to 0 (so it looked like the below screenshot), restarted the array, stopped the array, added cache drives back, restarted the array in maintenance mode

 

image.thumb.png.fc38eb79e9e756980a90d0ebdf66a756.png

 

Couple questions:

1. Was this the correct way to remove/re-add the cache pool?

2. The next step in the filesystem check is to run the btrfs check without the --readonly option, is there anything else I should do before this to ensure I don't cause further issues?

 

I suspect a power loss was the root cause, the devices exist so I doubt an ssd hardware issue, (this was run while in maintenance mode)

btrfs fi show
Label: none  uuid: b9325cba-fcee-4e86-8250-caa493fa4a24
        Total devices 2 FS bytes used 99.92GiB
        devid    1 size 238.47GiB used 143.03GiB path /dev/sdb1
        devid    2 size 238.47GiB used 143.03GiB path /dev/sdc1

 

After restarting in maintenance mode this is the output of the the filesystem check

btrfs check --readonly /dev/sdb1
Opening filesystem to check...
Checking filesystem on /dev/sdb1
UUID: b9325cba-fcee-4e86-8250-caa493fa4a24
[1/7] checking root items
[2/7] checking extents
data extent[178439438336, 16384] referencer count mismatch (root 5 owner 260 offset 513245184) wanted 0 have 1
data extent[178439438336, 16384] bytenr mimsmatch, extent item bytenr 178439438336 file item bytenr 0
data extent[178439438336, 16384] referencer count mismatch (root 5 owner 260 offset 34872983552) wanted 1 have 0
backpointer mismatch on [178439438336 16384]
ERROR: errors found in extent allocation tree or chunk allocation
[3/7] checking free space tree
[4/7] checking fs roots
[5/7] checking only csums items (without verifying data)
[6/7] checking root refs
[7/7] checking quota groups skipped (not enabled on this FS)
found 107287035904 bytes used, error(s) found
total csum bytes: 50747720
total tree bytes: 141934592
total fs tree bytes: 66371584
total extent tree bytes: 16416768
btree space waste bytes: 21003679
file data blocks allocated: 191448006656
 referenced 93518864384




btrfs check --readonly /dev/sdc1
Opening filesystem to check...
Checking filesystem on /dev/sdc1
UUID: b9325cba-fcee-4e86-8250-caa493fa4a24
[1/7] checking root items
[2/7] checking extents
data extent[178439438336, 16384] referencer count mismatch (root 5 owner 260 offset 513245184) wanted 0 have 1
data extent[178439438336, 16384] bytenr mimsmatch, extent item bytenr 178439438336 file item bytenr 0
data extent[178439438336, 16384] referencer count mismatch (root 5 owner 260 offset 34872983552) wanted 1 have 0
backpointer mismatch on [178439438336 16384]
ERROR: errors found in extent allocation tree or chunk allocation
[3/7] checking free space tree
[4/7] checking fs roots
[5/7] checking only csums items (without verifying data)
[6/7] checking root refs
[7/7] checking quota groups skipped (not enabled on this FS)
found 107287035904 bytes used, error(s) found
total csum bytes: 50747720
total tree bytes: 141934592
total fs tree bytes: 66371584
total extent tree bytes: 16416768
btree space waste bytes: 21003679
file data blocks allocated: 191448006656
 referenced 93518864384



system: Unraid 6.12.13 on an older i5-3570K system.

 

unraid-diagnostics-20241021-1238.zip

Edited by whomstdve
clarified question

Solved by JorgeB

  • Community Expert

Data corruption is being detected on both pool devices, you should run memtest, then type:

 

btrfs rescue zero-log /dev/sdb1

 

And see if it mounts.

  • Author

memtest did find a singular error, so unfortunately a hardware issue is likely present (the generated report is attached)

 

btrfs rescue zero-log /dev/sdb1

The above command gave no output, checking with lsblk gave

NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINTS
loop0    7:0    0  63.4M  1 loop /lib
loop1    7:1    0 339.2M  1 loop /usr
loop2    7:2    0     1G  0 loop /etc/libvirt
sda      8:0    1   7.3G  0 disk 
└─sda1   8:1    1   7.3G  0 part /boot
sdb      8:16   0 238.5G  0 disk 
└─sdb1   8:17   0 238.5G  0 part 
sdc      8:32   0 238.5G  0 disk 
└─sdc1   8:33   0 238.5G  0 part 
sdd      8:48   0   7.3T  0 disk 
└─sdd1   8:49   0   7.3T  0 part 
sde      8:64   0   7.3T  0 disk 
└─sde1   8:65   0   7.3T  0 part 
sdf      8:80   0   7.3T  0 disk 
└─sdf1   8:81   0   7.3T  0 part 
md1p1    9:1    0   7.3T  0 md   /mnt/disk1
md2p1    9:2    0   7.3T  0 md   /mnt/disk2
sr0     11:0    1  1024M  0 rom  

 

After rebooting post-memtest-ing the server I noticed the same ssd's are surprisingly shown in 2 places

1. in the cache pool

image.thumb.png.7cccacdb56ac911c98e36d3fa27897a2.png

2. in unassigned devices

image.thumb.png.68e16af7fa82c9afbb1ba354fbf1e8c4.png

 

MemTest86-Report-20241022-150839.html

  • Community Expert
  • Solution

Before trying anything else you need to replace the RAM.

  • 2 weeks later...
  • Author

I managed to find some spare DDR3 that passed multiple memtest runs, so we should be all good to go! Both original ram sticks had a single corruption issue.

Any thoughts on if recovery of the cache drives is possible? Not sure since the RAM was probably at fault.

  • Community Expert

Post new diags after array start, and the output from 

 

btrfs fi show

 

  • Author
btrfs fi show
Label: none  uuid: b9325cba-fcee-4e86-8250-caa493fa4a24
        Total devices 2 FS bytes used 99.92GiB
        devid    1 size 238.47GiB used 120.03GiB path /dev/sdb1
        devid    2 size 238.47GiB used 120.03GiB path /dev/sdc1

Looks like it worked (mostly), 120gb used instead of 143 originally, but I can browse the file explorer and although the logs had some errors I think they were mostly benign and not btrfs-related. Thanks for all your hlep

unraid-diagnostics-20241101.zip

  • Community Expert

Run a correcting scrub on the pool and post the results.

  • Author
UUID:             b9325cba-fcee-4e86-8250-caa493fa4a24
Scrub started:    Fri Nov  1 12:13:30 2024
Status:           finished
Duration:         0:03:27
Total to scrub:   211.59GiB
Rate:             1.02GiB/s
Error summary:    csum=4
  Corrected:      0
  Uncorrectable:  4
  Unverified:     0

 

  • Community Expert

Look in the syslog for the list of corrupt file(s), delete them or restore from a backup, then run another scrub to confirm 0 errors.

  • Author

Restored corrupted files, scrubbed, 0 errors!

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