On 09/28/2012 10:13 PM, Hugo Mills wrote:

quoted

Summary:

quoted

     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