BTRFS raid6 unmountable after a couple of days of usage.
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Quoted 12 lines · Austin S Hemmelgarn
Quoted 11 lines · Austin S Hemmelgarn
So, after experiencing this same issue multiple times (on almost a dozen different kernel versions since 4.0) and ruling out the possibility of it being caused by my hardware (or at least, the RAM, SATA controller and disk drives themselves), I've decided to report it here.
The general symptom is that raid6 profile filesystems that I have are working fine for multiple weeks, until I either reboot or otherwise try to remount them, at which point the system refuses to mount them.
Quoted 5 lines
Further updates, I just tried mounting the filesystem from the image above again, this time passing device= options for each device in the FS, and it seems to be working fine now. I've tried this with the other filesystems however, and they still won't mount.
I have experienced a similar problem on a raid1 with kernels from 3.17 onward following a kernel panic.
I have found that passing the other device as the main device to mount will often work.
E.g.
# mount -o device=/dev/sdb,device=/dev/sdc /dev/sdb /mountpoint open_ctree failed
# mount -o device=/dev/sdb,device=/dev/sdc /dev/sdc /mountpoint mounts correctly.
If I then do an immediate umount and try again I get the same thing, but after some time using the filesystem, I can umount and either device is working for the mount again.