Re: [Qemu-devel] [RFC PATCH 0/2] GlusterFS support in QEMU - v2

["Daniel P. Berrange" <berrange@redhat.com>]

On Sat, Jul 21, 2012 at 01:59:17PM +0530, Bharata B Rao wrote:
> Hi,
> 
> Here is the v2 patchset for supporting GlusterFS protocol from QEMU.
> 
> This set of patches enables QEMU to boot VM images from gluster volumes.
> This is achieved by adding gluster as a new block backend driver in QEMU.
> Its already possible to boot from VM images on gluster volumes, but this
> patchset provides the ability to boot VM images from gluster volumes by
> by-passing the FUSE layer in gluster. In case the image is present on the
> local system, it is possible to even bypass client and server translator and
> hence the RPC overhead.
> 
> The major change in this version is to not implement libglusterfs based
> gluster backend within QEMU but instead use libgfapi. libgfapi library
> from GlusterFS project provides APIs to access gluster volumes directly.
> With the use of libgfapi, the specification of gluster backend from QEMU
> matches more closely with the GlusterFS's way of specifying volumes. We now
> specify the gluster backed image like this:
> 
> -drive file=gluster:server@port:volname:image
> 
> - Here 'gluster' is the protocol.
> - 'server@port' specifies the server where the volume file specification for
>   the given volume resides. 'port' is the port number on which gluster
>   management daemon (glusterd) is listening. This is optional and if not
>   specified, QEMU will send 0 which will make libgfapi to use the default
>   port.
> - 'volname' is the name of the gluster volume which contains the VM image.
> - 'image' is the path to the actual VM image in the gluster volume.

I don't think we should be using '@' as a field separator here, when ":"
can do that job just fine. In addition we already have a precendent set
with the sheepdog driver for using ':' for separating all fields:

  -drive file=sheepdog:example.org:6000:imagename

If you want to allow for port number to be omitted, this can be handled
thus:

  -drive file=sheepdog:example.org::imagename

which is how -chardev deals with omitted port numbers

Regards,
Daniel
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