Interpreting `btrfs filesystem show'
Hello, all
While trying to resolve free space problems, and found that I cannot interpret the output of:
Quoted 1 line
btrfs filesystem show
Label: none uuid: 8971ce5b-71d9-4e46-ab25-ca37485784c8
Total devices 1 FS bytes used 34.06GiB
devid 1 size 40.00GiB used 37.82GiB path /dev/sda2
How come the total used value is less than the value listed for the only device?
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Quoted 5 lines · Anton Shepelev
Hello, all
While trying to resolve free space problems, and found that I cannot interpret the output of:
Quoted 8 lines
Quoted 1 line
btrfs filesystem show
Label: none uuid: 8971ce5b-71d9-4e46-ab25-ca37485784c8
Total devices 1 FS bytes used 34.06GiB
devid 1 size 40.00GiB used 37.82GiB path/dev/sda2How come the total used value is less than the value listed for the only device?
"Used" on the device is the mount of space allocated. "Used" on the
FS is the total amount of actual data and metadata in that allocation.
You will also need to look at the output of "btrfs fi df" to see
the breakdown of the 37.82 GiB into data, metadata and currently unused.
See https://btrfs.wiki.kernel.org/index.php/FAQ#Understanding_free_space.2C_using_the_original_tools for the details.
Hugo.
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Hugo Mills | "Your problem is that you have a negative hugo@... carfax.org.uk | personality." http://carfax.org.uk/ | "No, I don't!" PGP: E2AB1DE4 | Londo and Vir, Babylon 5
Quoted 8 lines · Hugo Mills
Quoted 7 lines · Anton Shepelev
Hello, all
While trying to resolve free space problems, and found that I cannot interpret the output of:
Quoted 1 line
btrfs filesystem show
Quoted 8 lines
Quoted 6 lines
Label: none uuid: 8971ce5b-71d9-4e46-ab25-ca37485784c8
Total devices 1 FS bytes used 34.06GiB
devid 1 size 40.00GiB used 37.82GiB path/dev/sda2How come the total used value is less than the value listed for the only device?
"Used" on the device is the mount of space allocated. "Used" on the
s/mount/amount/
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FS is the total amount of actual data and metadata in that allocation.
You will also need to look at the output of "btrfs fi df" to see
the breakdown of the 37.82 GiB into data, metadata and currently unused.See https://btrfs.wiki.kernel.org/index.php/FAQ#Understanding_free_space.2C_using_the_original_tools for the details.
Hugo.
Signature · 4 lines
Hugo Mills | "Your problem is that you have a negative hugo@... carfax.org.uk | personality." http://carfax.org.uk/ | "No, I don't!" PGP: E2AB1DE4 | Londo and Vir, Babylon 5
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Hugo Mills to Anton Shepelev:
Quoted 16 lines
Quoted 11 lines
While trying to resolve free space problems, and found that I cannot interpret the output of:
Quoted 1 line
btrfs filesystem show
Label: none uuid: 8971ce5b-71d9-4e46-ab25-ca37485784c8
Total devices 1 FS bytes used 34.06GiB
devid 1 size 40.00GiB used 37.82GiB path/dev/sda2How come the total used value is less than the value listed for the only device?
"Used" on the device is the mount of space allocated.
"Used" on the FS is the total amount of actual data and metadata in that allocation.
Quoted 6 lines
You will also need to look at the output of "btrfs fi
df" to see the breakdown of the 37.82 GiB into data, metadata and currently unused.See
https://btrfs.wiki.kernel.org/index.php/FAQ#Understanding_free_space.2C_using_the_original_tools for the details
Thank you, Hugo, understood. mount/amount is a very fitting typo :-)
Does the standard `du' tool work correctly for btfrfs?
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Quoted 22 lines · Anton Shepelev
Hugo Mills to Anton Shepelev:
Quoted 20 lines
Quoted 11 lines
While trying to resolve free space problems, and found that I cannot interpret the output of:
Quoted 1 line
btrfs filesystem show
Label: none uuid: 8971ce5b-71d9-4e46-ab25-ca37485784c8
Total devices 1 FS bytes used 34.06GiB
devid 1 size 40.00GiB used 37.82GiB path/dev/sda2How come the total used value is less than the value listed for the only device?
"Used" on the device is the mount of space allocated.
"Used" on the FS is the total amount of actual data and metadata in that allocation.You will also need to look at the output of "btrfs fi
df" to see the breakdown of the 37.82 GiB into data, metadata and currently unused.
Quoted 8 lines
Quoted 2 lines
See
https://btrfs.wiki.kernel.org/index.php/FAQ#Understanding_free_space.2C_using_the_original_tools for the detailsThank you, Hugo, understood. mount/amount is a very fitting typo :-)
Does the standard `du' tool work correctly for btfrfs?
For the default 'physical usage' mode, it functionally does not work correctly, because it does not know about reflinks. The easiest way to see this is to create a couple of snapshots of a subvolume alongside the subvolume, and then run du -s --totals on those snapshots and the subvolume. It will report the total space usage to be equal to the sum of the values reported for each snapshot and the subvolume, when it should instead only count the space usage for shared data once.
For the 'apparent usage' mode provided by the GNU implementation, it does work correctly.
Hugo Mills - 15.10.18, 16:26:
Quoted 15 lines · Anton Shepelev
Quoted 5 lines
Hello, all
While trying to resolve free space problems, and found that
I cannot interpret the output of:
Quoted 8 lines
Quoted 1 line
btrfs filesystem show
Label: none uuid: 8971ce5b-71d9-4e46-ab25-ca37485784c8 Total devices 1 FS bytes used 34.06GiB
devid 1 size 40.00GiB used 37.82GiB path/dev/sda2How come the total used value is less than the value listed for the only device?
Quoted 7 lines
"Used" on the device is the mount of space allocated. "Used" on the
FS is the total amount of actual data and metadata in that allocation.You will also need to look at the output of "btrfs fi df" to see
the breakdown of the 37.82 GiB into data, metadata and currently unused.
I usually use btrfs fi usage -T, cause
1. It has all the information.
2. It differentiates between used and allocated.
% btrfs fi usage -T /
Overall:
Device size: 100.00GiB
Device allocated: 54.06GiB
Device unallocated: 45.94GiB
Device missing: 0.00B
Used: 46.24GiB
Free (estimated): 25.58GiB (min: 25.58GiB)
Data ratio: 2.00
Metadata ratio: 2.00
Global reserve: 70.91MiB (used: 0.00B)
Data Metadata System
Id Path RAID1 RAID1 RAID1 Unallocated
-- ------------------------ -------- --------- -------- -----------
2 /dev/mapper/msata-debian 25.00GiB 2.00GiB 32.00MiB 22.97GiB 1 /dev/mapper/sata-debian 25.00GiB 2.00GiB 32.00MiB 22.97GiB
-- ------------------------ -------- --------- -------- -----------
Total 25.00GiB 2.00GiB 32.00MiB 45.94GiB
Used 22.38GiB 754.66MiB 16.00KiB
For RAID it in some place reports the raw size and sometimes the logical size. Especially in the "Total" line I find this a bit inconsistent. "RAID1" columns show logical size, "Unallocated" shows raw size.
Also "Used:" in the global section shows raw size and "Free (estimated):" shows logical size.
Thanks
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Martin