As I mentioned in an earlier post, I was thinking of using KVM in a production environment. I've done some performance testing recently, and here is some thinge I've discovered:

• "virtio_net" has great performance.
• "virtio_blk" has really poor (write) performance.
• There seems to be a bug with virtio and >3.5G memory in a guest.

I did some performance testing (bonnie/dd) and got 40M/sec in write performance using virtio in the guest. I got 260M/s natively in the host, This is a known issue, and the developers hope to get fixes in during the 2.6.26 timeframe.