[Gluster-users] Bricks as BTRFS

[Ric Wheeler]

On 09/26/2014 01:58 PM, James wrote:
> On Thu, Sep 25, 2014 at 2:53 AM, Venky Shankar <vshankar at redhat.com> wrote:
>> Hey folks,
>>
>> Wanted to check if anyone out here uses BTRFS (and willing to share their
>> experiences[1]) as the backend filesystem for GlusterFS. We're planning to
>> explore some of it's features and put it to use for GlusterFS. This was
>> discussed briefly during the weekly meeting on #gluster-meeting[2].
>>
>> To start with, we plan to explore data/metadata checksumming (+ scrubbing)
>> and subvolumes to "offload" the work to BTRFS. The mentioned features would
>> help us with BitRot detection[3] and Openstack Manila use cases respectively
>> (though there are various other nifty things one would want to do with
>> them).
>>
>> Thanks in advance!
>
> Hey,
>
> I couldn't make the meeting, but I am interested in BTRFS. I added
> this in puppet-gluster a bunch of months ago as a feature branch.
>
> https://bugzilla.redhat.com/show_bug.cgi?id=1094860
>
> I just pushed it to git master.
>
> https://github.com/purpleidea/puppet-gluster/commit/6c962083d8b100dcaeb6f11dbe61e6071f3d13f0
>
> The reason I want btrfs support, is I want glusterfs to eventually be
> able to support reflinks across gluster volumes. There is a strong use
> case for this feature.
>
> Let me know if this helps!
> Cheers,
> James
>

Reflinks in btrfs (or ocfs2) need to be between files in the same linux kernel 
instance of btrfs.  Effectively, we have two inodes backed by the same physical 
blocks.

It won't, in general, be useful for reflinks across volumes....

Regards,

Ric