Re: kvm + ceph performance issues

[Wolfgang Hennerbichler <wolfgang.hennerbichler@risc-software.at>]

On 03/08/2013 09:35 AM, Stefan Hajnoczi wrote:

> Please try using virtio-blk instead of IDE.

there is no difference if I use virtio-blk.

> If the guest still jerks try using the Linux rbd block driver instead of
> QEMU -drive rbd:.  I haven't used Ceph much but there should be
> documentation on attaching a RADOS block device to your Linux host.
> Tell QEMU to use the RADOS block device like a regular file (you are now
> using the kernel driver instead of QEMU code to talk to the Ceph
> cluster).

This doesn't work yet on the linux-kernel with format 2 images. Format 2
is capable of read/write snapshots and cooler cloning-stuff. I need this
for backup-reasons.

> Please let us know the outcome.  If you find that virtio-blk does not
> make much difference but using the kernel rbd driver does, then this
> suggests there is a bug in QEMU's block/rbd.c.

I'm pretty sure there is, other ceph users reported the same problems
that I've found. The ceph developers are looking into it.

> Stefan

Wolfgang