On 2014-12-04 09:13, Austin S Hemmelgarn wrote:
> On 2014-12-04 08:53, Shriramana Sharma wrote:
>> I observe that whenever I create a BtrFS instance using mkfs.btrfs,
>> there is always the leftover cruft of two System/Metadata-Single
>> allocation profiles:
>>
>> btrfs fi df /run/media/samjnaa/BRIHATII/
>> Data, single: total=460.01GiB, used=458.47GiB
>> System, DUP: total=8.00MiB, used=80.00KiB
>> System, single: total=4.00MiB, used=0.00B
>> Metadata, DUP: total=1.50GiB, used=736.86MiB
>> Metadata, single: total=8.00MiB, used=0.00B
>> GlobalReserve, single: total=256.00MiB, used=0.00B
>>
>> Doing btrfs balance eventually removes these (but since I forgot to do
>> it *before* copying 400+ G of data to the drive it's still running)
>> but I don't understand why these have to be created in the first
>> place? (I just used SuSE Tumbleweed's default mkfs.btrfs without any
>> -m or -d options.)
>>
> SuSE may have an old version of btrfs-progs then (which wouldn't
> surprise me, it is an 'enterprise' distribution after all), because I
> haven't seen this on anything since 3.16.
Correction, this happens even on current versions, I just hadn't noticed 
it.  It also seems to create a data chunk in single mode when data is 
set to some other profile.
>
> The really interesting thing in this case is that the metadata chunk is
> 8M, when they are usually 256M.
>
> Also, for future reference, you can use the switch -mprofiles=single to
> just balance out those chunks.
>