On Wed, Jan 08, 2014 at 10:51:16PM +0100, Javi Legido wrote:
> I'm experiencing bad performance on every I/O intensive action, such
> as clone a VM or when the guest updates packages via apt.
>
> I'm using a Directory pool [1] with qcow2 files since I like the
> ability to perform snapshots. Reading some literature looks like a
> Filesystem pool [2] plus raw disk images is the best combination in
> terms of disk performance.
>
> Can somebody please confirm or contradict?
Usually LVM ('logical') offers the best disk performance. But at that
point you are working with logical volumes instead of regular files.
Some tools like backup applications may require regular files.
If LVM doesn't suit your needs then raw image files do indeed offer the
good performance.
Also try:
* virtio-blk instead of IDE or SCSI
<target dev='vda' bus='virtio'/>
* Linux AIO for local disks/files
<driver name="qemu" io="native" ... />
* cache=none (O_DIRECT)
<driver name="qemu" cache="none" ... />
If you still experience poor performance, please run a disk benchmark
(like fio) on both guest and host to compare performance. Make sure the
benchmark uses O_DIRECT to avoid the page cache.
Stefan
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
