On Wed, Oct 31, 2007 at 02:56:53PM +0200, Dan Kenigsberg wrote: > On Wed, Oct 31, 2007 at 11:17:23AM +0100, Laurent Vivier wrote: > > Dan Kenigsberg a écrit : > > >Hi, > > > > > >I have some newby's questions: is a speedup expected, comparing to ide > > > > We should have a speedup. > > Would you suggest where it could show? I was trying simple dd and > bonnie++, and saw big variace between consequtive runs, but little > change between mounting an image with if=ide and if=scsi. Was I doing > something wrong?
Using dd is pretty useless as a benchmark. bonnie++ can work sometimes if you tune the size of its I/O ops wrt to the amount of RAM in your host and guest. The big variance is likely caused by doing small enough I/O that the cache in either host or guest can buffer your data at times. IOZone is a benchmark I find gives better results, though it does take a hell of a long time to run. Tune IOZone params to do increasingly large I/O chunks, so that it will exceed RAM in both host & guest & let it repeat many times & you should get to some stable benchmark results. There were some results at the last Xen summit comparing the IDE & SCSI drivers in QEMU(KVM) against Xen paravirt - the SCSI results were very impressive & significantly ahead of IDE. http://xen.org/files/xensummit_4/xen_summit_2007_spring_hvm_charts_Harper.pdf Regards, Dan. -- |=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=| |=- Perl modules: http://search.cpan.org/~danberr/ -=| |=- Projects: http://freshmeat.net/~danielpb/ -=| |=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=|