I have a Qemu-KVM host system setup on CentOS 6.3. Four 1TB SATA HDDs working in Software RAID10. Guest CentOS 6.3 is installed on separate LVM. People say that they see guest performance almost equal to host performance, but I don't see that. My i/o tests are showing 30-70% slower performance on guest than on host system. I tried to change scheduler (set elevator=deadline on host and elevator=noo
![KVM guest io is much slower than host io: is that normal?](https://cdn-ak-scissors.b.st-hatena.com/image/square/1d7824625a3ecbc3a39062b14aaa9db8a44aa022/height=288;version=1;width=512/https%3A%2F%2Fcdn.sstatic.net%2FSites%2Fserverfault%2FImg%2Fapple-touch-icon%402.png%3Fv%3D9b1f48ae296b)