Hi,
I just tried the virtio block device with the intent
to boost disk throughput for my vm.
I ran bonnie++ -r 512 -s 2048 -u nobody -d /tmp:
Version 1.03 ------Sequential Output------ --Sequential Input- --Random-
-Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP
virtio_blk 2G 14274 42 20206 14 22363 37 31116 92 66731 81 140.8 13
kvm-ide 2G 26065 83 26435 28 24146 33 26587 84 57991 18 91.5 2
The host is a Xeon 3040, 1G RAM (I know that that is a bit
few, it's just a test machine...), the vm gets 512MB of that.
The data is stored on two SATA disks, mirrored (RAID1) with
md, lvm running on top of that.
Host and Client are running 2.6.25-0.200.rc8.git3.i686. This
is a kernel from Fedora-Rawhide with kvm manually enabled by me.
KVM version is 64.
Especially writing seems to be slower using virtio, but
reading isn't that much faster.
I thought virtio would improve io speed significantly because
of fewer steps needed to communicate betweeen host and client.
What might be the reason that I can't see a speed boost?
- Wrong setup (The virtio-client boots from /dev/vda1,
so I think virtio is working)
- virtio_blk is not matured/tuned enough to give a real
speed boost
- I'm missing a patch that is not included into 2.6.26-rc8
but can be found in kvm-git
- The output of bonnie++ is bogus because timing is not that
accurate within a kvm-client
Any ideas welcome.
Kind regards,
Gerd
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