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Re: [Xen-devel] 2.4.29-xenU VBD performance (problem)

Ian Pratt wrote:

But, under domU (2.4.29-xenU), using that same lvm-volume as VBD, I only get around 10 - 12 MB/sec write performance measured in the same way.

That's very odd -- I see virtually no loss of throughput in a domU.

However, 100MB isn't really enough to get a decent measure as its likely to all 
still be in memory -- sync doesn't do what you think. I usually do measurements 
using a transfer size of 10x the memory of the system.

A couple of other things to try if you still experience poor peformance:
  * use a 2.6 domU
  * use a raw partition rather than LVM

We do most of our testing using 2.6 for everything, so its possible there a 
weird 2.4 domU to 2.6 dom0 performance bug.

Right. And to some extent, comparing 2.4 to 2.6 is
a bit of an apples to oranges comparison. There are
other differences in the kernel path - not just the
virtual block driver coming out of domU.


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