[libvirt-users] bad IO on VM

[Stefan G. Weichinger]

Am 09.02.2012 15:01, schrieb Daniel P. Berrange:
> On Thu, Feb 09, 2012 at 10:35:02AM +0100, Akendo wrote:
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>> I have to create some VM. I using KVM for it, manage by libvirtd. The
>> problem of my is that the IO is  very bad. I'm nut sure, but I using
>> currently vmdk. Could this be the problem?
> 
> I think that is a very likely suspect. The only drivers in QEMU
> that have had any serious performance tuning are QCow2 and raw.
> The vmdk driver is not really actively maintained beyond bug
> fixing.  I'd strongly recommend you try just 'raw' file formats
> instead for maximum performance, and make sure you use 'cache=none'
> for the disks too.

Let me repeat my question from the other thread here:

I wasn't able to set "cache=none", the libvirt(?) complained.

0.9.8, btw.

What might be the reason?