On Fri, Jul 31, 2009 at 11:59:50AM +0100, Gavin Conway wrote:
> > Why do you need HVM guest? HVM, aka fully virtualized guests use Qemu
> > to _emulate_ IDE (or SCSI) adapters and disks, so that'll be slow.
> >
> > If you can't switch to paravirtual (PV) guests, at least try to
> > install
> > PV-on-HVM drivers, which should help a lot. Other possibility is to
> > use
> > stubdoms with HVM, but that's not available in Xen shipped in CentOS
> > 5.3.
> > Stubdoms can be found from Xen 3.4.x
> >
> > PV guests will be a lot faster, since there's no need for emulation.
> > I recommend you to run PV guests.
>
> Hi Pasi,
>
> We get the same performance under windows but comparing the difference
> between
> the two it's easier to demonstrate with 2 x Linux systems. With regards to
> why we use HVM,
> this is so we can do P2V migrations of various OS' into Xen.
>
For windows you should use PV-on-HVM drivers aswell, check the GPLPV drivers.
That way you'll get a LOT better performance.
You can do Linux P2V to PV guest aswell, no need to run HVM.
> Could you link me to the PV-on-HVM drivers for Linux, these sound like a good
> way forward.
> Also Stubdoms are a new one on me, do you know of any recommended reading.
> Googling draws up a blank apart from problems people have had.
>
http://blog.xen.org/index.php/2008/08/28/xen-33-feature-hvm-device-model-domain/
http://www.xen.org/files/xensummitboston08/SamThibault_XenSummit.pdf
Check those out.
-- Pasi
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