performance comparison host openvz kvm

[marius]

hello

have done some tests now and wondering why the kvm harddisk is so slow

dd if=/dev/zero of=/tmp/500mb count=1400k
running dd 5x times to get "real" average results

results:
host system 140-145mb/s
openvz - turnkey fileserver 130-145mb/s
kvm - turnkey fileserver 35-40 mb/s

kvm vm installed from iso
virtio drivers for hdd
2gb ram
1cpu 2 cores

host system is a amd dual core x2 260u
1tb sata hdd

any suggestions ?

 

[udo]

hello

have done some tests now and wondering why the kvm harddisk is so slow

dd if=/dev/zero of=/tmp/500mb count=1400k
running dd 5x times to get "real" average results

results:
host system 140-145mb/s
openvz - turnkey fileserver 130-145mb/s
kvm - turnkey fileserver 35-40 mb/s

kvm vm installed from iso
virtio drivers for hdd
2gb ram
1cpu 2 cores

host system is a amd dual core x2 260u
1tb sata hdd

any suggestions ?

Hi Marius,
you measuring cache-speed (and of course the host will win, because have much more ram)!
And the io-speed on kvm is slower than the host (and need cpu-power).

To get comparable values use something like this:

dd if=/dev/zero of=bigfile bs=1024k count=8192 conv=fdatasync
# drop caches
echo 3 > /proc/sys/vm/drop_caches
# read
dd if=bigfile of=/dev/null bs=1024k

Udo

 

[tom]

post you VMID.conf file (from the kvm - turnkey fileserver 35-40 mb/s)

 

[marius]

okay, tested again ....

dd if=/dev/zero of=bigfile bs=1024k count=8192 conv=fdatasync

host system 93 mb/s
kvm 71 mb/s

71mb/s is a good value for the beginning

continue testing and expecting better results with hdd passtrough