On 09/28/2012 10:13 PM, Hugo Mills wrote:
Summary:
> Disk_size: 135.00 GiB
> Disk_allocated: 10.51 GiB
> Disk_unallocated: 124.49 GiB
> Used: 2.59 GiB
> Free_(Estimated): 91.93 GiB
> Average_disk_efficiency: 70 %
>
> Details:
> Chunk-type Mode Disk-allocated Used Available
> 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:
> Disk-allocated -> space used on the disk by the chunk
> Disk-size -> size of the disk
> Disk-unallocated -> disk not used in any chunk
> Used -> space used by the files/metadata
The problem here is that if you're using raw storage, the Used
value in the second stanza grows twice as fast as the user expects.
This is the misunderstanding whom I talked before.
If you give a look at the line "Metadata DUP", you can see that the
disk-allocated are about 6GB, instead if you sum Used and Available you
got 3GB.
I.e. if you create a 1GB file, "Used" ever increased of 1GB, and
Available ever decrease 1GB, whichever you are using DUP or Single or RAID*
I
think this second stanza should at minimum include the "cooked" values
used in btrfs fi df, because those reflect the user's experience. Then
adding [some of?] the raw values you've got here to help connect the
values to the raw data in the first stanza of output.
The only raw values are the one "prefixed" with disk. The other ones are
at the net of the DUP/Single/Raid....
As I said above, it's the connection between "I wrote a 1GiB file
to my filesystem" and "why have my numbers increased/decreased by
2GiB(*)/1.2GiB(**)?"
I repeat, if the chunk is DUP-ed, if you create 1GB file:
- Disk-allocate increase 2GB (supposing that all the chunks are full)
- Used increase 1GB
- Available decrease 1GB
(*) RAID-1
(**) RAID-5-ish
Ciao
Goffredo
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