Xen users - May 2007 - Xen HD performance

Hi,

Can anyone point me to some information about the behaviour of Xen
concerning Disk I/O.

What happens on my computer is that whenever I activate Xen, the I/O
capability of my hard drives is divided by the number of Xen virtual
machines.

So, if I use the disk as much as possible on one VM, the other VMs
don''t
seem affected. I guess this can be seen as a feature, but I am wondering
whether it is possible to tweak this behaviour. 

I''d like to reserve *some* I/O for the other VMs, but if they are idle,
I''d like one VMs to take the unused resources.
Is that possible ?

Thanks for your help,
Sami Dalouche


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Sami Dalouche wrote:
> Hi,
>
> Can anyone point me to some information about the behaviour of Xen
> concerning Disk I/O.
>
> What happens on my computer is that whenever I activate Xen, the I/O
> capability of my hard drives is divided by the number of Xen virtual
> machines.
>   
Even when the other domains are not busy? I mean, disk I/O bandwidth and 
bandwidth to the disk controller has to be shared, but if only one 
domain is using it, I''d expect it to be disk bound: disk I/O is 
expensive in a virtualized environment, but it shouldn''t cost *too*
much
if hte guest domains are not churning the disk.


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