Re: [Xen-devel] poor domU VBD performance.

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Sun, Mar 27, 2005 at 06:41:27PM +0100, Ian Pratt wrote:
> > I found out that dom0 does file-system IO and raw IO ( using 
> > dd as a tool to test
> > throughput from the disk ) is about exactly the same as when 
> > using a standard 
> > linux kernel without XEN. But the raw IO from DomU to an 
> > unused disk ( a second
> > disk in the system ) is limited to fourty percent of the 
> > speed I get within Dom0.
> 
> Just to be clear: you're doing a dd performance test within dom0 to the
> exact same partition on the 2nd disk that you're using when you start
> the domU and finding that the domU 'dd' performance is 40% of the dom0
> performance?
> 
> I've not heard of anyone else having problems like this. What happens if
> you use a partition on the 1st disk?
> 
> What chipset is the IDE controller? What device (e.g. sda1) are you
> exporting the disk partition into the domU as?
> 
> Are you sure dom 0 is idle when doing the dd test in the domU?
> 

I reported same kind of problems earlier too. 

2.4 domU is really slow (1/3 speed of 2.6 dom0), 2.6 domU is faster, but not 
even close 
to the speed of 2.6 dom0.

My tests were on top lvm over sw-raid5.

-- Pasi Kärkkäinen
       
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                           .Next.Generation.


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