Hello,
I got a problem with btrfs running out of space (not THE
Internet-wide, well known issues with interpretation).
The problem is: something eats the space while not running anything that
justifies this. There were 18 GB free space available, suddenly it
dropped to 8 GB and then to 63 MB during one night. I recovered 1 GB
with rebalance -dusage=5 -musage=5 (or sth about), but it is being eaten
right now, just as I'm writing this e-mail:
/dev/sda2 64G 63G 452M 100% /
/dev/sda2 64G 63G 365M 100% /
/dev/sda2 64G 63G 316M 100% /
/dev/sda2 64G 63G 287M 100% /
/dev/sda2 64G 63G 268M 100% /
/dev/sda2 64G 63G 239M 100% /
/dev/sda2 64G 63G 230M 100% /
/dev/sda2 64G 63G 182M 100% /
/dev/sda2 64G 63G 163M 100% /
/dev/sda2 64G 64G 153M 100% /
/dev/sda2 64G 64G 143M 100% /
/dev/sda2 64G 64G 96M 100% /
/dev/sda2 64G 64G 88M 100% /
/dev/sda2 64G 64G 57M 100% /
/dev/sda2 64G 64G 25M 100% /
while my rough calculations show, that there should be at least 10 GB of
free space. After enabling quotas it is somehow confirmed:
# btrfs qgroup sh --sort=excl /
qgroupid rfer excl
-------- ---- ----
0/5 16.00KiB 16.00KiB
[30 snapshots with about 100 MiB excl]
0/333 24.53GiB 305.79MiB
0/298 13.44GiB 312.74MiB
0/327 23.79GiB 427.13MiB
0/331 23.93GiB 930.51MiB
0/260 12.25GiB 3.22GiB
0/312 19.70GiB 4.56GiB
0/388 28.75GiB 7.15GiB
0/291 30.60GiB 9.01GiB <- this is the running one
This is about 30 GB total excl (didn't find a switch to sum this up). I
know I can't just add 'excl' to get usage, so tried to pinpoint the
exact files that occupy space in 0/388 exclusively (this is the last
snapshots taken, all of the snapshots are created from the running fs).
Now, the weird part for me is exclusive data count:
# btrfs sub sh ./snapshot-171125
[...]
Subvolume ID: 388
# btrfs fi du -s ./snapshot-171125
Total Exclusive Set shared Filename
21.50GiB 63.35MiB 20.77GiB snapshot-171125
How is that possible? This doesn't even remotely relate to 7.15 GiB
from qgroup.~The same amount differs in total: 28.75-21.50=7.25 GiB.
And the same happens with other snapshots, much more exclusive data
shown in qgroup than actually found in files. So if not files, where
is that space wasted? Metadata?
btrfs-progs-4.12 running on Linux 4.9.46.
best regards,
--
Tomasz Pala <gotar@xxxxxxxxxxxxx>
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