[libvirt-users] bad IO on VM

[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.

Daniel
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