Am 13.04.2015 um 14:28 hat ein geschrieben: > Dear Fam, > > Check out my update please: > http://lists.nongnu.org/archive/html/qemu-devel/2015-04/msg01318.html > > Using aio=native,cache=none results in 500%-2000% performance drop comparing > to > bare metal and 300%-1000% comparing to aio=threads,cache=unsafe.
cache=unsafe isn't really useful to compare against because it throws all flush requests away. If your benchmark includes disk flushes, you're only cheating yourself with this mode. It's generally accepted that cache=none,aio=native is the best configuration for such scenarios. Also make sure to use the right guest configuration; for example, using the right I/O scheduler can make a major difference for Linux guests. Not sure how to configure Windows for best performance, maybe someone else can help with that. If you insist on cheating and would like to combine both, you could give 'cache=none,cache.no-flush=on,aio=native' a try. Kevin
