real free space on btrfs volume (performance impact)
Hello
we are currently investigating performance issue on system runing
above btrs filesystem. Is it possible, that performance is impacted by lack of free space? Also, how to get info about real free space on btrfs volume?
# btrfs-show /dev/sdb1
Label: opt uuid: 28a55827-e677-47a9-98d5-d31eb3d71436
Total devices 1 FS bytes used 167.83GB
devid 1 size 240.00GB used *229.25GB* path /dev/sdb1Btrfs Btrfs v0.19
# btrfs filesystem df /opt Data: total=213.23GB, used=165.26GB System, DUP: total=8.00MB, used=40.00KB System: total=4.00MB, used=0.00 Metadata, DUP: total=8.00GB, used=2.57GB
# df -h /opt Filesystem Size Used Avail Use% Mounted on /dev/sdb1 240G 171G 59G 75% /opt
How come that there is difference detween btrfs-show and df .. 40GB Is the space really usead or can I claim it back? (there are no snapshots)
# btrfs subvolume list /opt #
Thanks
michal
2012/1/10 Michal Suba <[email protected]>:
Quoted 3 lines
Hello
=A0we are currently investigating performance issue on system runing =
above
Quoted 1 line
btrs filesystem. Is it possible, that performance is impacted by lack=
of
Quoted 1 line
free space? Also, how to get info about real free space on btrfs volu=
me?
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# btrfs-show /dev/sdb1 Label: opt =A0uuid: 28a55827-e677-47a9-98d5-d31eb3d71436 =A0 =A0Total devices 1 FS bytes used 167.83GB =A0 =A0devid =A0 =A01 size 240.00GB used *229.25GB* path /dev/sdb1Btrfs Btrfs v0.19
# btrfs filesystem df /opt Data: total=3D213.23GB, used=3D165.26GB System, DUP: total=3D8.00MB, used=3D40.00KB System: total=3D4.00MB, used=3D0.00 Metadata, DUP: total=3D8.00GB, used=3D2.57GB
Quoted 5 lines
# df -h /opt Filesystem =A0 =A0 =A0 =A0 =A0 =A0Size =A0Used Avail Use% Mounted on /dev/sdb1 =A0 =A0 =A0 =A0 =A0 =A0 240G =A0171G =A0 59G =A075% /optHow come that there is difference detween btrfs-show and df .. 40GB I=
s the
Quoted 5 lines
space really usead or can I claim it back? (there are no snapshots)
# btrfs subvolume list /opt #
The btrfs-show command is being deprecated. It's output can be easy to misunderstand, but it probably won't be corrected since it's going away at some point.
Basically, what this is telling you is that 229.25GB is "committed" (213.23GB Data + 2 x8.00GB Metadata (because it's duplicated) + 2 x 8.00MB System.
However, all the "committed" space is not being used (which is clearer in the 'btrfs filesystem df' command).
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Quoted 4 lines · Mitch Harder
2012/1/10 Michal Suba <[email protected]>:
Quoted 3 lines
Hello
=C2=A0we are currently investigating performance issue on system run=
ing above
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btrs filesystem. Is it possible, that performance is impacted by lac=
k of
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free space? Also, how to get info about real free space on btrfs vol=
ume?
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# btrfs-show /dev/sdb1 Label: opt =C2=A0uuid: 28a55827-e677-47a9-98d5-d31eb3d71436 =C2=A0 =C2=A0Total devices 1 FS bytes used 167.83GB =C2=A0 =C2=A0devid =C2=A0 =C2=A01 size 240.00GB used *229.25GB* path=
/dev/sdb1
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Btrfs Btrfs v0.19
# btrfs filesystem df /opt Data: total=3D213.23GB, used=3D165.26GB System, DUP: total=3D8.00MB, used=3D40.00KB System: total=3D4.00MB, used=3D0.00 Metadata, DUP: total=3D8.00GB, used=3D2.57GB# df -h /opt Filesystem =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0Size =C2=A0Used =
Avail Use% Mounted on
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/dev/sdb1=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 240G =C2=A0171G =
=C2=A0 59G =C2=A075% /opt
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How come that there is difference detween btrfs-show and df .. 40GB =
Is the
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space really usead or can I claim it back? (there are no snapshots)
# btrfs subvolume list /opt #The btrfs-show command is being deprecated. =C2=A0It's output can be =
easy
Quoted 2 lines
to misunderstand, but it probably won't be corrected since it's going away at some point.
The output of "btrfs fi show /dev/whatever" is identical, and isn't going away afaik. That said, it is easy to misinterpret, although that's probably unavoidable while still actually presenting that information.
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