Disk Benchmark results, kvm-69

[Henrik Holst <henrik@witsbits.com>]

We have performed some quick benchmarks against kvm-69 on an Intel Q6600
with 8GB RAM and equipped with 4 SATA drives (Maxtor DiamondMax 10
6V300F0).

During these tests we noticed a problem with the virtio block device in
where it completely locks the drive after a while when running on a smp
guest. The other disks are ok and the guest is working as it should but
all access to /dev/vda1 never times out.

Also with if=scsi the host would output (during the bonnie++ tests):
	lsi_scsi: error: PRDERED queue not implemented
	lsi_scsi: error: Unimplemented message 0x0c

Host: 2.6.24-1-amd64 debian testing
Guest: 2.6.24-16-server ubuntu 8.04

hdparm -tT /dev/sdb on host:
	Timing cached reads: 3845.63 MB/sec
	Timing buffered disk reads: 67.98 MB/sec

Qemu invocation (for virtio):
	qemu-system-x86_64
	-m 3072 -smp 4 \
	-drive file=ubuntu.img,if=ide,boot=on,media=disk \
	-drive file=/dev/sdb,if=virtio,boot=off,cache=off,media=disk

Bonnie++ invocation:
	bonnie++ -r 512 -s 2048 -u root -d /mnt/sdb1/ :

Results:
---------------------------------------------------------------------------------
Version 1.03b       ------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
host             2G 60814  81 83149  15 64419   8 85187  99 2394159 100 +++++ +++
guest-ide        2G 65048  89 72621  13 64792   9 84224  99 2311183  99 +++++ +++
guest-scsi       2G 67387  90 73757  13 63783   9 84645 100 2297687  99 +++++ +++
guest-virtio     2G 41564  57 73274  28 62725  27 71656  85 2441544  98 +++++ +++ (This is with -smp 1)

There seams to be no major performance difference between ide and scsi while virtio is not to be recommended at this moment.
All in all the IO looks very close to native, at least with this limited tests.

/Henrik Holst