On Tue, Apr 10, 2012 at 6:25 PM, Michael Baysek <mbaysek@xxxxxxxxxxxxx> wrote: > Well, I'm trying to determine which I/O method currently has the very least performance overhead and gives the best performance for both reads and writes. > > I am doing my testing by putting the entire guest onto a ramdisk. I'm working on an i5-760 with 16GB RAM with VT-d enabled. I am running the standard Centos 6 kernel with 0.12.1.2 release of qemu-kvm that comes stock on Centos 6. The guest is configured with 512 MB RAM, using, 4 cpu cores with it's /dev/vda being the ramdisk on the host. Results collected for ramdisk usually do not reflect the performance you get with a real disk or SSD. I suggest using the host/guest configuration you want to deploy. > I've been using iozone 3.98 with -O -l32 -i0 -i1 -i2 -e -+n -r4K -s250M to measure performance. I haven't looked up the options but I think you need -I to use O_DIRECT and bypass the guest page cache - otherwise you are not benchmarking I/O performance but overall file system/page cache performance. Stefan -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
