[Fedora-xen] expected disk performance?

[Ben]

I'm running 1 domU on my dom0, and both are largely idle. They're running on a 
dualcore Opeteron, so I don't suspect the cpu is the bottleneck.

I'm using phy: in my domU config.

I notice (with large scp copies, at least) that writing to the domU starts off 
at network speed, but then slows down to about 2MB/s after ~10 seconds, 
presumably as buffers fill up. Looking at vmstat on the domU shows 100% cpu 
wait, and on the dom0 at the same time, I see almost 100% idle, with the 
occasional 1% system.

Have any of you tweaked your xen scheduling?

On Tue, 23 May 2006, Stephen C. Tweedie wrote:

> Hi,
>
> On Tue, 2006-05-23 at 08:55 -0700, Ben wrote:
>> Well, this gives me hope that I'm suffering from some kind of
>> misconfiguration issue. I'm using LVM-backed domUs, and I see
>> dom0 hdparm-t: 53.68 MB/sec
>> domU hdparm -t: 18.39 MB/sec
>
> "top" and "xm top", perhaps?  If you have fast storage and slow CPUs,
> you may be seeing the system struggle to keep the IO pipeline between
> domU and dom0 full enough to saturate the disk, for example.
>
> Another thing, are you using "phy:" or "file:" on the domU config?
>
> --Stephen
>
>
>