On 09/27/2012 12:44 PM, Sébastien Maury wrote:
Hi,
I've installed a new server using btrfs for my root partition ("/").
It uses snapper for snapshots management and all seems to work pretty fine.
My problem is to be able to know the remaining REAL free space in my
partition.
Using different commands, i have different results, and i don't know how
to interpret them correctly :
poivron:~ # btrfs filesystem df /
Data: total=4.01GB, used=2.16GB
System, DUP: total=8.00MB, used=4.00KB
System: total=4.00MB, used=0.00
Metadata, DUP: total=3.00GB, used=429.16MB
Metadata: total=8.00MB, used=0.00
In effect the output of "btrfs filesystem df /" is not very friendly.
What about changing the output as below:
$ btrfs filesystem disk-free /
Summary:
Total: 135.00GB
Allocated: 10.51GB
Unallocated: 124.49GB
Free_(Estimated) 86.56GB
Average_disk_efficiency: 62 %
Details:
Chunk-type Mode Allocated Used Free
---------- ---- --------- -------- ---------
Data Single 4.01GB 2.16GB 1.87GB
System DUP 16.00MB 4.00KB 7.99MB
System Single 4.00MB 0.00 4.00MB
Metadata DUP 6.00GB 429.16MB 2.57GB
Metadata Single 8.00MB 0.00 8.00MB
Where the "Free_(Estimated)" and "Average_disk_efficency" are computed as:
Average_disk_efficency = ratio of average disk usage =
(sum(ChunkUsed)+sum(ChunkFree))/sum(ChunkAllocated)
Estimated_available = Average_disk_efficency *
Unallocated+sum(ChunkFree)
I am open to suggestion about the terms: Used vs Allocated and Free vs
Available, or a better description of "Average disk efficiency"
BR
G.Baroncelli
P.S. the source could be find at
http://cassiopea.homelinux.net/git/btrfs-progs-unstable.git
branch
disk_free
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