[sheepdog-users] sheep and no compression object files putted on btrfs & zfs

[Marcin Mirosław]

W dniu 01.06.2015 o 15:59, Hitoshi Mitake pisze:
> At Wed, 27 May 2015 14:00:06 +0200,
> Marcin Mirosław wrote:
>>
>> Hi!
>> I'd like to reanimate my old question. I put sheep on btrfs mounted with
>> compress-force=lzo. Files created manually (using dd from /dev/zero) are
>> compressed very well on this filesystem, as expected. When I create vdi,
>> write zeroes to vdi then disk usage on btrfs grows at the same level as
>> summary size of files created by sheep.
>> It means that btrfs, even with compress-force, doesn't compress files.
>> What is the reason of this behavior? How can I change it and allow btrfs
>> to compress files?
>> I did test on zfs, it works corrrectly, zfs compressed files without
>> problem.
> 
> I don't know the detail of the btrfs compression feature. But sheep
> creates object files with fallocate() for better disk layout. It would
> be preventing compression, I guess.


Hi!
It looks you guessed correctly:
http://www.spinics.net/lists/linux-btrfs/msg40067.html
http://comments.gmane.org/gmane.comp.file-systems.btrfs/27896

Thanks for idea!
Marcin