Re: [Xen-users] Xen Partition Performance

[Matt Ayres <matta@xxxxxxxxxxxx>]

Steve Dobbelstein wrote:
> "Sylvain Coutant" <sco@xxxxxxxxxx> wrote on 04/25/2006 07:47:09 AM:
>
> > > I'm setting up a Xen system since I have diferent choices to
> > > create the domU's partitions: raw partition, lvm, files.
> > >
> > > I've done some tests with hdparm and it all seems to be the same.
> > It can if you have enough CPU in dom0. The interesting point could
> > then be : how much each of those cost in CPU share in dom0 ? The
> > less layers you'll have, the better it should behave. Raw partition
> > should be the cheapest, closely followed by LVM and lastly files
> > (which could have different results depending on fs in use: ext2,
> > ext3, reiser, xfs, etc.). I'm not sure if the difference would be
> > very significant. Probably, it depends on usage, number of domUs, ...
> Also be aware that the devices go through the buffer cache on dom0.  I
> would not be surprised that the performance to a partition, LVM volume, or
> loop device is not that different, since they all hit the buffer cache,
> especially if your tests do mostly reads.
I have to disagree here.  A physical partition / LVM gets directly 
passed to the domU and by-passes the dom0 buffer cache.  Since the image 
(loop) file resides on the host that will be cached by dom0.
Thanks,
Matt Ayres

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