Hi Stefan.
Many thanks for the tips. I already was doing all that you mentioned
except LVM and raw files. Let me try this and let's see what happens.
Thanks.
On 9 January 2014 03:58, Stefan Hajnoczi <stefanha@xxxxxxxxx> wrote:
> 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
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