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Re: KVM disk performance


Hi Diego,

Thanks for your quick response.

Yes we are using the virtio drivers. We have to add them manual for FreeBSD & Windows, and it works. Only the performance is very bad.

Kind regards,


On Mar 26, 2012, at 3:43 PM, Diego Parrilla wrote:

> Have you tried virtio for storage?
> http://www.linux-kvm.org/page/Virtio
> Enviado desde mi iPhone, perdona la brevedad
> El 26/03/2012, a las 14:59, Martin van Wilderen - JDN BV <martin@xxxxxx> escribió:
>> Hi List,
>> I have a question about KVM disk performance. We are using Openstack Nova on three machines. These machines have a SSD drive with a dd write performance of about 130mb/s
>> Within the instance the write performance is down to about 5 mb/s. When using the allocate trick (dd zero to disk before newfs) we get a performance of 20 mb/s.
>> Things a have tried but don't give any extra results are:
>> - Settings the disklayout from qcow2 to raw
>> - Settings the cache type in libvirt.xml (writeback, writethrough, none)
>> - Switching KSM on and off.
>> - Tested with different guests OS, Linux, FreeBSD, Windows.
>> Is there someone who had some extra info i can check? Or are there more people with this issue?
>> Snippet from libvirt.xml
>> <driver type='qcow2'/ cache='writeback'/>
>> <source file='/var/lib/nova/instances/instance-00000113/disk'/>
>> <target dev='vda' bus='virtio'/>
>> Kind regards,
>> Martin
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