[Xen-users] Re: Windows Disk performance

[Christian Tramnitz <chris.ace@xxxxxxx>]

Ruslan Sivak schrieb:
> I'm using a 3ware 9650 with 4 10k VelociRaptors in raid 5.  I doubt that 
> it's reading out of cache, I'm probably getting sequential reads from 
> the outside of the disks with readahead and all that fun stuff. 
Russ,

if you are talking about getting max speed out of a 3Ware including 
optimizing read-ahead and caching/buffering that's fine, but you started 
the topic comparing dom0 vs domU performance and asking if your testing 
method is flawed... it is!
hdparm will give you a nice output, but that has nothing in common with 
real throughput that you will get when running tools like bonnie++, 
iozone or iometer.
The theoretical maximum I would expect from your setup is something 
between 200-240MB/s sustained read transfer rate and 150-180MB/s write 
transfer rate.
But transfer rate is not everything, when talking about performance you 
may want to look for I/O operations per second.
I would strongly suggest that you use the exact same tools in dom0 and 
domU to measure their performance difference and only compare that if 
you interesting in any domU/GPLPV vs. domU/stock vs. dom0 performance 
conclusions.
That being said, I'm very interested in the results, I will also do some 
testing with iometer in dom0 and domU, PV and HVM (stock and GPLPV), 
maybe we can ask the community for some feedback regarding common 
iometer test parameters that we should use and then gather the results 
to get ideas.
Best regards,
   Christian


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