[Gluster-users] QEMU-KVM-libgfapi question

[Stefan Hajnoczi]

On Fri, Nov 15, 2013 at 6:48 PM, Nicholas Majeran
<nmajeran at suntradingllc.com> wrote:
> I am running a KVM test cluster on Fedora 19 using gluster + libgfapi as a
> network backend for my QCOW2 images.
> This configuration precludes me from using virsh's backup features provided
> in Fedora and thus I am doing "live snapshots" by executing:
>
> # perform internal snapshot on qcow2 using FUSE mount to gluster:
> qemu-img snapshot -c snapname /gluster/test.qcow2
>
> # convert the snapshot to an external file for archiving:
> qemu-img convert -s snapname /gluster/test.qcow2
> /gluster-backup/test.qcow2.snapshot
>
> My Question:
>
> 1. Is there any blocking or locking issues I should be concerned about while
> doing snapshot's or converts?
>
> 2. I know this leaves my snapshot in an inconsistent state...but is this an
> incorrect use of the qemu/qcow2 tools?

Accessing the image file from another process while the VM is running
is not support and could corrupt the image file.

> 3. Is there a better way to do this via gluster / gfapi that I'm missing?

If you use LVM on the bricks you can use the block device translator
(bd_map) which supports LVM snapshots.

Stefan