On 05/17/2012 11:05 PM, Itamar Heim wrote:
On 05/17/2012 06:55 PM, Bharata B Rao wrote:
On Wed, May 16, 2012 at 3:29 PM, Itamar Heim<ih...@redhat.com>  wrote:
On 05/15/2012 07:35 PM, Andrei Vakhnin wrote:

Yair

Thanks for an update. Can I have KVM hypervisors also function as storage nodes for glusterfs? What is a release date for glusterfs support? We're
looking for a production deployment in June. Thanks


current status is
1. patches for provisioning gluster clusters and volumes via ovirt are in
review, trying to cover this feature set [1].
I'm not sure if all of them will make the ovirt 3.1 version which is slated
to branch for stabilization June 1st, but i think "enough" is there.
so i'd start trying current upstream version to help find issues blocking you, and following on them during june as we stabilize ovirt 3.1 for release
(planned for end of june).

2. you should be able to use same hosts for both gluster and virt, but there
is no special logic/handling for this yet (i.e., trying and providing
feedback would help improve this mode).
I would suggest start from separate clusters though first, and only later
trying the joint mode.

3. creating a storage domain on top of gluster:
- expose NFS on top of it, and consume as a normal nfs storage domain
- use posixfs storage domain with gluster mount semantics
- future: probably native gluster storage domain, up to native
  integration with qemu

I am looking at GlusterFS integration with QEMU which involves adding
GlusterFS as block backend in QEMU. This will involve QEMU talking to
gluster directly via libglusterfs bypassing FUSE. I could specify a
volume file and the VM image directly on QEMU command line to boot
from the VM image that resides on a gluster volume.

Eg: qemu -drive file=client.vol:/Fedora.img,format=gluster

In this example, Fedora.img is being served by gluster and client.vol
would have client-side translators specified.

I am not sure if this use case would be served if GlusterFS is
integrated as posixfs storage domain in VDSM. Posixfs would involve
normal FUSE mount and QEMU would be required to work with images from
FUSE mount path ?

With QEMU supporting GlusterFS backend natively, further optimizations
are possible in case of gluster volume being local to the host node.
In this case, one could provide QEMU with a simple volume file that
would not contain client or server xlators, but instead just the posix
xlator. This would lead to most optimal IO path that bypasses RPC
calls.

So do you think, this use case (QEMU supporting GlusterFS backend
natively and using volume file to specify the needed translators)
warrants a specialized storage domain type for GlusterFS in VDSM ?

I'm not sure if a special storage domain, or a PosixFS based domain with enhanced capabilities.
Ayal?

Related Question:
With QEMU using GlusterFS backend natively (as described above), it also means that it needs addnl options/parameters as part of qemu command line (as given above).

How does VDSM today support generating a custom qemu cmdline. I know VDSM talks to libvirt, so is there a framework in VDSM to edit/modify the domxml based on some pre-conditions, and how / where one should hook up to do that modification ? I know of libvirt hooks framework in VDSM, but that was more for temporary/experimental needs, or am i completely
wrong here ?

Irrespective of whether GlusterFS integrates into VDSM as PosixFS or special storage domain it won't address the need to generate a custom qemu cmdline if a file/image was served by
GlusterFS. Whats the way to address this issue in VDSM ?

I am assuming here that special storage domain (aka repo engine) is only to manage image repository, and image related operations, won't help in modifying qemu cmd line being generated.

[Ccing vdsm-devel also]

thanx,
deepak


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