On 2018-10-17 00:14, Dmitry Katsubo wrote:
As a workaround I can monitor dmesg output but:
1. It would be nice if I could tell btrfs that I would like to mount
read-only
after a certain error rate per minute is reached.
2. It would be nice if btrfs could detect that both drives are not
available and
unmount (as mount read-only won't help much) the filesystem.
Kernel log for Linux v4.14.2 is attached.
I wonder if somebody could further advise the workaround. I understand
that running
btrfs volume over USB devices is not good, but I think btrfs could play
some role
as well.
In particular I wonder if btrfs could detect that all devices in RAID1
volume became
inaccessible and instead of reporting increasing "write error" counter
to kernel log simply
render the volume as read-only. "inaccessible" could be that if the same
block cannot be
written back to minimum number of devices in RAID volume, so btrfs gives
up.
Maybe someone can advise some sophisticated way of quick checking that
filesystems is
healthy? Right now the only way I see is to make a tiny write (like
create a file and
instantly remove it) to make it die faster... Checking for write IO
errors in "btrfs
dev stats /mnt/backups" output could be an option provided that delta is
computed for
some period of time and write errors counter increase for both devices
in the volume
(as apparently I am not interested in one failing block which btrfs
tries to write
again and again increasing the write errors counter).
Thanks for any feedback.
--
With best regards,
Dmitry
