I have two physical servers with Ubuntu 10.04 server on them. They are connected with a 1Gbps card over a gigabit switch. Each of these host servers has one Win 2008 guest VM. Both VMs are well provisioned (4 cores, 12GB RAM), RAW disks.

My asp.net/sql server applications are running much slower compared to very similar physical setups.

Both machines are setup to use virtio for disk and network. I used iperf to check network performance and I get: Physical host 1 -----> Physical Host 2: 957 Mbits/sec Physical host 1 -----> Win 08 Guest 1: 557 Mbits/sec Win 08 Guest 1 -----> Phy host 1: 182 Mbits/sec Win 08 Guest 1 -----> Win 08 Guest 2: 111 Mbits /sec

My app is running on Win08 Guest 1 and Guest 2 (web and db). There is a huge drop in network throughput (almost 90%) between the two guest. Further the throughput does not seem to be symmetric between host and guest as well.

The CPU utilization on the guests and hosts is less than 2% right now (we are just testing right now).

Apart from this, there have been random slow downs in the network to as low as 1 Mbits/sec making the whole application unusable.

Any help to trouble shoot this would be appreciated.