At 02/08/2017 12:44 AM, Vasco Visser wrote:
Hello,
My system is or seems to be running out of disk space but I can't find
out how or why. Might be a BTRFS peculiarity, hence posting on this
list. Most indicators seem to suggest I'm filling up, but I can't
trace the disk usage to files on the FS.
The issue is on my root filesystem on a 28GiB ssd partition (commands
below issued when booted into single user mode):
$ df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda3 28G 26G 2.1G 93% /
$ btrfs --version
btrfs-progs v4.4
$ btrfs fi usage /
Overall:
Device size: 27.94GiB
Device allocated: 27.94GiB
Device unallocated: 1.00MiB
So from chunk level, your fs is already full.
And balance won't success since there is no unallocated space at all.
The first 1M of btrfs is always reserved and won't be allocated, and 1M
is too small for btrfs to allocate a chunk.
Device missing: 0.00B
Used: 25.03GiB
Free (estimated): 2.37GiB (min: 2.37GiB)
Data ratio: 1.00
Metadata ratio: 1.00
Global reserve: 256.00MiB (used: 0.00B)
Data,single: Size:26.69GiB, Used:24.32GiB
You still have 2G data space, so you can still write things.
/dev/sda3 26.69GiB
Metadata,single: Size:1.22GiB, Used:731.45MiB
Metadata has has less space when considering "Global reserve".
In fact the used space would be 987M.
But it's still OK for normal write.
/dev/sda3 1.22GiB
System,single: Size:32.00MiB, Used:16.00KiB
/dev/sda3 32.00MiB
System chunk can hardly be used up.
Unallocated:
/dev/sda3 1.00MiB
$ btrfs fi df /
Data, single: total=26.69GiB, used=24.32GiB
System, single: total=32.00MiB, used=16.00KiB
Metadata, single: total=1.22GiB, used=731.48MiB
GlobalReserve, single: total=256.00MiB, used=0.00B
However:
$ mount -o bind / /mnt
$ sudo du -hs /mnt
9.3G /mnt
Try to balance:
$ btrfs balance start /
ERROR: error during balancing '/': No space left on device
Am I really filling up? What can explain the huge discrepancy with the
output of du (no open file descriptors on deleted files can explain
this in single user mode) and the FS stats?
Just don't believe the vanilla df output for btrfs.
For btrfs, unlike other fs like ext4/xfs, which allocates chunk
dynamically and has different metadata/data profile, we can only get a
clear view of the fs from both chunk level(allocated/unallocated) and
extent level(total/used).
In your case, your fs doesn't have any unallocated space, this make
balance unable to work at all.
And your data/metadata usage is quite high, although both has small
available space left, the fs should be writable for some time, but not long.
To proceed, add a larger device to current fs, and do a balance or just
delete the 28G partition then btrfs will handle the rest well.
Thanks,
Qu
Any advice on possible causes and how to proceed?
--
Vasco
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
