Re: 2.4.29-xenU VBD performance (problem)

[Nivedita Singhvi <niv@us.ibm.com>]

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.

thanks,
Nivedita



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