Yeah, true, rereading it he is not clear about whether he has run the software on xen on the same box he ran raw on, although it is implied. It is a very different question on EC2.
* On EC2 I've tried the c1.xlarge and the giant cc1.4xlarge. With cc1.4xlarge, I saw maybe a ~10% increase accept() rate. * Two separate, virtualized servers at the office. * A private, virtualized server on Rackspace was briefly tested as well.
A compilation of netperf results are available at https://gist.github.com/985475