[Fedora-xen] expected disk performance?

[Stephen C. Tweedie]

Hi,

On Tue, 2006-05-23 at 11:54 +0100, Stephen C. Tweedie wrote:

> On Mon, 2006-05-22 at 20:26 -0700, Ben wrote:
> > Today I upgraded to the new xen and kernel packages that just came  
> > out, as I'd been looking forward to all the IO cleanup supposedly in  
> > xen 3.0.2. Imagine my disappointment when I found out that my domU's  
> > virtual disks still seem to be throttled at around 2MB/s sustain  
> > writes for some reason. My dom0 is "much" better at ~14MB/s sustained  
> > writes.
> 
> Are you using a file or device-backed virtual device?

On two local guests on a rawhide box:

 Device-backed guest (LVM on fast SATA disk):
  dom0 hdparm -t:	53.70 MB/sec
  domU hdparm -t:	53.61 MB/sec

 File-backed guest:
  dom0 hdparm -t:	85.7138 MB/sec
  domU hdparm -t:	75.2901 MB/sec

(The file is a sparse file that's only about 50% full, so there's
actually less data being read in that case.)

The file-backed domain definitely takes a lot more dom0 CPU time to
serve, but they are both pretty fast.

Cheers,
 Stephen