Hello Everyone,

Within the last few days, Fix Common Problems (FCP) has been reporting "unable to write to cache".  There are 2 cache drives and they both appear to be fine and there is plenty of space.  The problem is preventing me from starting my Docker containers.

I've taken a look at the logs and while it's easy to find the effects of the issue, I couldn't find the cause.  Admittedly, this is my first real problem with Unraid.

Any help would be appreciated.

Spenny
 

server-diagnostics-20241104-0608.zip

It definitely looks like you have corruption in your docker.img file:

Nov  3 04:16:03 Server kernel: BTRFS warning (device loop2): csum failed root 5 ino 5476243 off 0 csum 0xf34e21bd expected csum 0x46e26f17 mirror 1
Nov  3 04:16:03 Server kernel: BTRFS error (device loop2): bdev /dev/loop2 errs: wr 252, rd 0, flush 0, corrupt 240274, gen 0
Nov  3 04:16:03 Server kernel: BTRFS warning (device loop2): csum failed root 5 ino 5476243 off 4096 csum 0x9ccb8b17 expected csum 0xf603cbd7 mirror 1
Nov  3 04:16:03 Server kernel: BTRFS error (device loop2): bdev /dev/loop2 errs: wr 252, rd 0, flush 0, corrupt 240275, gen 0
Nov  3 04:16:03 Server kernel: BTRFS warning (device loop2): csum failed root 5 ino 5476243 off 0 csum 0xf34e21bd expected csum 0x46e26f17 mirror 1
Nov  3 04:16:03 Server kernel: BTRFS error (device loop2): bdev /dev/loop2 errs: wr 252, rd 0, flush 0, corrupt 240276, gen 0

I would suggest that you start by doing the following:

• running a scrub on the cache pool to see if it says its file system is corrupt.
• running a memtest as RAM issues are a common cause of btrfs issues.

at the very least you are then going to need to recreate the docket.img file and then reinstall your docker containers via Apps->Previous Apps (to get them with settings intact).

 

When I try to run a scrub, the status is aborted instantly.  I tried it in the terminal after it appeared to do nothing in the GUI.

 

btrfs scrub start /mnt/cache
scrub started on /mnt/cache, fsid 73f2f644-baca-4da2-8a42-a14f2afa9a79 (pid=575250)
Starting scrub on devid 1
Starting scrub on devid 2

btrfs scrub status /mnt/cache
UUID:             73f2f644-baca-4da2-8a42-a14f2afa9a79
Scrub started:    Mon Nov  4 05:29:26 2024
Status:           aborted
Duration:         0:00:00
Total to scrub:   585.90GiB
Rate:             0.00B/s
Error summary:    no errors found

 

Pool is going read-only suggest backing up and re-formatting, but before that run memtest, since btrfs was detecting data corruption on both devices:

 

Nov  3 04:15:52 Server kernel: BTRFS info (device nvme1n1p1): bdev /dev/nvme1n1p1 errs: wr 0, rd 0, flush 0, corrupt 360, gen 0
Nov  3 04:15:52 Server kernel: BTRFS info (device nvme1n1p1): bdev /dev/nvme0n1p1 errs: wr 0, rd 0, flush 0, corrupt 359, gen 0

 

Many thanks to both JorgeB and itimpi. Before doing any work, I started the memtest.  Well, guess what? One of the DIMMS is failing.

I will rebuild my cache from backup and (hopefully) call it a day.