Follow up on “btrfs free space. It’s complicated. Still.”
Posted by jpluimers on 2019/02/14
In the mean time I’ve made a bit of progress on btrfs free space. It’s complicated. Still.
Let me start with an example system that has details further below.
- total of quotas is slightly more than 1.1 Gibibyte
- Sometimes this helps making the quota list better:
btrfs quota rescan /
- Sometimes this helps making the quota list better:
- the disk partition itself is 10 Gibibyte
- btrfs indicates there is 6.6 Gibibyte used
- df indicates there is 11 Gigabyte total, 6.9 Gigabyte used and 2.6 Gigabyte available.
In short: the used 6.6 Gibibyte (which matches 6.9 Gigabyte) does not match the 11 Gibibyte. A situation very similar to [WayBack] Disk usage is more than double the snapshots exclusive data — Linux BTRFS.
Reminder to self: try
bedupthat is supposed to deduplicate btrfs data: [WayBack] Re: Disk usage is more than double the snapshots exclusive data — Linux BTRFS
- Repository g2p/bedup: Btrfs deduplication
- Not sure which package is needed (
bedup,python3-bedupnorburpare found)
I need to check out on de-duplication (as I know this particular machine has quite a bit of duplicate data).
But first lets get the size down a bit with this series of commands:
sftp-host:~ # btrfs balance start -dusage=0 -musage=0 /
Done, had to relocate 0 out of 18 chunks
sftp-host:~ # btrfs balance start -dusage=10 -musage=10 /
Done, had to relocate 1 out of 18 chunks
sftp-host:~ # btrfs balance start -dusage=20 -musage=20 /
Done, had to relocate 1 out of 18 chunks
sftp-host:~ # btrfs balance start -dusage=30 -musage=30 /
Done, had to relocate 2 out of 18 chunks
sftp-host:~ # btrfs balance start -dusage=40 -musage=40 /
Done, had to relocate 1 out of 17 chunks
sftp-host:~ # btrfs balance start -dusage=50 -musage=40 /
Done, had to relocate 2 out of 17 chunks
sftp-host:~ # btrfs balance start -dusage=60 -musage=40 /
Done, had to relocate 2 out of 17 chunks
sftp-host:~ # btrfs balance start -dusage=60 -musage=60 /
sftp-host:~ # btrfs filesystem show
Label: none uuid: 6492a1c6-5fbc-4938-bf11-57d6194e6b8f
Total devices 1 FS bytes used 6.61GiB
devid 1 size 10.00GiB used 8.88GiB path /dev/sda2
sftp-host:~ # btrfs filesystem df /
Data, single: total=7.82GiB, used=6.35GiB
System, DUP: total=32.00MiB, used=16.00KiB
Metadata, DUP: total=512.00MiB, used=263.47MiB
GlobalReserve, single: total=22.67MiB, used=0.00B
Compare this to the initial situation:
sftp-host:~ # btrfs filesystem show
Label: none uuid: 6492a1c6-5fbc-4938-bf11-57d6194e6b8f
Total devices 1 FS bytes used 6.61GiB
devid 1 size 10.00GiB used 10.00GiB path /dev/sda2
sftp-host:~ # btrfs filesystem df /
Data, single: total=8.94GiB, used=6.35GiB
System, DUP: total=32.00MiB, used=16.00KiB
Metadata, DUP: total=512.00MiB, used=264.27MiB
GlobalReserve, single: total=23.48MiB, used=0.00B
Now you see that:
- far less of the partition is actually used by the filesystem (was 10 Gibibyte, now 8.88 Gibibyte)
- far less storage is needed for the data (was 8.94 Gibibyte, now 7.82 Gibibyte to store 6.35 Gibibyte)
If the above succeeds
Continue with steps closer to 99 (which is a percentage) and if that succeeds try this:
btrfs balance start --full-balance /
In my experience it needs at least 60% free dh -f disk space to run to completion. If it fails, it’s no problem: it merges the final almost full blocks. But those blocks will be split soon anyway because of file system write activity.
Nicer overview
You can even get a nicer view by executing btrfs filesystem usage -T / (which I did after continuing up to 99):
Overall:
Device size: 10.00GiB
Device allocated: 8.22GiB
Device unallocated: 1.78GiB
Device missing: 0.00B
Used: 7.00GiB
Free (estimated): 2.72GiB (min: 1.83GiB)
Data ratio: 1.00
Metadata ratio: 2.00
Global reserve: 24.55MiB (used: 48.00KiB)
Data Metadata System
Id Path single DUP DUP Unallocated
-- --------- ------- --------- -------- -----------
1 /dev/sda2 7.41GiB 768.00MiB 64.00MiB 1.78GiB
-- --------- ------- --------- -------- -----------
Total 7.41GiB 384.00MiB 32.00MiB 1.78GiB
Used 6.47GiB 269.88MiB 16.00KiB
If the above fails
Three things to try now:
- Try to start with lower values of
-dusageand-musage. - Split
-dusageand-musagein differentbtrfs balance startcommands. - Try to remove any snapper snapshots that you do not need.
Log:
sftp-host:~ # df -h
Filesystem Size Used Avail Use% Mounted on
devtmpfs 176M 0 176M 0% /dev
tmpfs 182M 0 182M 0% /dev/shm
tmpfs 182M 868K 181M 1% /run
tmpfs 182M 0 182M 0% /sys/fs/cgroup
/dev/sda2 11G 6.9G 2.6G 73% /
/dev/sda2 11G 6.9G 2.6G 73% /var/spool
/dev/sda2 11G 6.9G 2.6G 73% /tmp
/dev/sda2 11G 6.9G 2.6G 73% /boot/grub2/i386-pc
/dev/sda2 11G 6.9G 2.6G 73% /boot/grub2/x86_64-efi
/dev/sda2 11G 6.9G 2.6G 73% /var/crash
/dev/sda2 11G 6.9G 2.6G 73% /var/lib/named
/dev/sda2 11G 6.9G 2.6G 73% /var/opt
/dev/sda2 11G 6.9G 2.6G 73% /var/lib/mailman
/dev/sda2 11G 6.9G 2.6G 73% /var/tmp
/dev/sda2 11G 6.9G 2.6G 73% /var/log
/dev/sda2 11G 6.9G 2.6G 73% /var/lib/pgsql
/dev/sda2 11G 6.9G 2.6G 73% /var/lib/machines
/dev/sda2 11G 6.9G 2.6G 73% /srv
/dev/sda2 11G 6.9G 2.6G 73% /usr/local
/dev/sda2 11G 6.9G 2.6G 73% /opt
/dev/sda2 11G 6.9G 2.6G 73% /.snapshots
/dev/sda3 5.5G 36M 5.5G 1% /home
tmpfs 37M 0 37M 0% /run/user/1000
sftp-host:~ # btrfs filesystem show
Label: none uuid: 6492a1c6-5fbc-4938-bf11-57d6194e6b8f
Total devices 1 FS bytes used 6.61GiB
devid 1 size 10.00GiB used 10.00GiB path /dev/sda2
sftp-host:~ # btrfs filesystem df /
Data, single: total=8.94GiB, used=6.35GiB
System, DUP: total=32.00MiB, used=16.00KiB
Metadata, DUP: total=512.00MiB, used=264.27MiB
GlobalReserve, single: total=23.48MiB, used=0.00B
sftp-host:~ # btrfs qgroup show /
qgroupid rfer excl
-------- ---- ----
0/5 16.00KiB 16.00KiB
0/257 1.05MiB 1.05MiB
0/258 2.55GiB 51.11MiB
0/259 2.36MiB 2.36MiB
0/260 16.00KiB 16.00KiB
0/261 16.00KiB 16.00KiB
0/262 16.00KiB 16.00KiB
0/263 36.00KiB 36.00KiB
0/264 16.00KiB 16.00KiB
0/265 16.00KiB 16.00KiB
0/266 16.00KiB 16.00KiB
0/267 16.00KiB 16.00KiB
0/268 16.00KiB 16.00KiB
0/269 533.83MiB 533.83MiB
0/270 16.00KiB 16.00KiB
0/271 48.00KiB 48.00KiB
0/272 16.00KiB 16.00KiB
0/289 16.00KiB 16.00KiB
0/401 2.80GiB 396.91MiB
0/402 2.55GiB 9.57MiB
0/403 2.55GiB 12.91MiB
0/404 2.54GiB 676.00KiB
0/405 2.54GiB 660.00KiB
0/406 2.81GiB 60.34MiB
0/407 2.55GiB 8.66MiB
0/408 2.55GiB 4.57MiB
0/409 2.56GiB 24.31MiB
0/410 2.55GiB 7.28MiB
0/411 2.57GiB 20.55MiB
255/289 16.00KiB 16.00KiB
sftp-host:~ # !~
~/Versioned/btrfs-size/btrfs-size.sh
===============================================================================================
Snapshot / Subvolume ID Total Exclusive Data
===============================================================================================
257 gen 505741 top level 5 path .snapshots 257 1.05MB 1.05MB
258 gen 505796 top level 257 path .snapshots/1/snapshot 258 2.55GB 51.11MB
259 gen 505736 top level 5 path boot/grub2/i386-pc 259 2.36MB 2.36MB
260 gen 452028 top level 5 path boot/grub2/x86_64-efi 260 16.00KB 16.00KB
261 gen 452028 top level 5 path opt 261 16.00KB 16.00KB
262 gen 505720 top level 5 path srv 262 16.00KB 16.00KB
263 gen 505791 top level 5 path tmp 263 36.00KB 36.00KB
264 gen 505717 top level 5 path usr/local 264 16.00KB 16.00KB
265 gen 452028 top level 5 path var/crash 265 16.00KB 16.00KB
266 gen 452028 top level 5 path var/lib/mailman 266 16.00KB 16.00KB
267 gen 452028 top level 5 path var/lib/named 267 16.00KB 16.00KB
268 gen 452028 top level 5 path var/lib/pgsql 268 16.00KB 16.00KB
269 gen 505795 top level 5 path var/log 269 533.83MB 533.83MB
270 gen 452028 top level 5 path var/opt 270 16.00KB 16.00KB
271 gen 505796 top level 5 path var/spool 271 48.00KB 48.00KB
272 gen 505771 top level 5 path var/tmp 272 16.00KB 16.00KB
289 gen 452028 top level 5 path var/lib/machines 289 16.00KB 16.00KB
401 gen 451786 top level 257 path .snapshots/92/snapshot 401 2.81GB 396.91MB
402 gen 465358 top level 257 path .snapshots/93/snapshot 402 2.55GB 9.57MB
403 gen 465363 top level 257 path .snapshots/94/snapshot 403 2.55GB 12.91MB
404 gen 471598 top level 257 path .snapshots/95/snapshot 404 2.54GB 676.00KB
405 gen 471603 top level 257 path .snapshots/96/snapshot 405 2.54GB 660.00KB
406 gen 471658 top level 257 path .snapshots/97/snapshot 406 2.81GB 60.34MB
407 gen 487231 top level 257 path .snapshots/98/snapshot 407 2.55GB 8.66MB
408 gen 490073 top level 257 path .snapshots/99/snapshot 408 2.55GB 4.57MB
409 gen 490081 top level 257 path .snapshots/100/snapshot 409 2.56GB 24.31MB
410 gen 505715 top level 257 path .snapshots/101/snapshot 410 2.55GB 7.28MB
411 gen 505739 top level 257 path .snapshots/102/snapshot 411 2.57GB 20.55MB
===============================================================================================
Exclusive Total: 1.11GB
sftp-host:~ #
–jeroen
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