Why does so much virt stuff depend on glusterfs?

[Peter Robinson]

On Tue, Jul 23, 2013 at 11:14 AM, Richard W.M. Jones <rjones at redhat.com> wrote:
> On Mon, Jul 22, 2013 at 08:26:18PM -0400, Matthew Miller wrote:
>> On Mon, Jul 22, 2013 at 05:17:01PM -0700, Adam Williamson wrote:
>> > Today in Absurd Dependency Bingo:
>> > >  glusterfs                       x86_64 3.4.0-2.fc19     @updates-testing 4.7 M
>> [...]
>> > >  qemu-common                     x86_64 2:1.4.2-4.fc19   @updates-testing 624 k
>>
>> $ rpm -q --changelog qemu-common
>> [...]
>> * Wed May 15 2013 Cole Robinson <crobinso at redhat.com> - 2:1.4.1-2
>> - Enable gluster support
>>
>> And then all the rest just falls out from there because they require qemu.
>>
>>
>> > >  vinagre                         x86_64 3.8.2-1.fc19     @side            3.0 M
>>
>> (This one requires spice.)
>>
>> At 4.7M glusterfs isn't exactly tiny, and is another one of these things
>> that's not so useful unless configured (even though that's awesomely easy);
>> maybe the libs could be split out?
>
> The problem is that qemu's block layer isn't a stable API with
> pluggable / loadable modules.  There's been some talk and even patches
> upstream trying making it so (at least, the loadable modules part, the
> stable API part will probably never happen).  But it's not done yet.
>
> qemu's internal block API:
> http://git.qemu.org/?p=qemu.git;a=blob;f=include/block/block_int.h;h=c6ac871e210ea21f91d799e44a102119048dde54;hb=HEAD#l83
>
> Therefore if you want to use qemu to access, in this case, a glusterfs
> cluster, then you have to compile qemu with gluster support, and that
> pulls in glusterfs.  We could compile it out, but then no one would be
> able to use gluster to store their virtual machines at all.
>
> Not sure if glusterfs could be split into client and server parts
> and/or if that would help (only a "client" bit is needed).

I thought gluster 3.4 was suppose to support a libgfapi which
integrated into qemu [1] so in theory the bare minimum qemu should
need is libgfapi.

[1] http://www.gluster.org/2013/07/glusterfs-3-4-is-here/