Networking performance is a critical part of the usability of any virtualized system. As such, several benchmarks have been published showing that a virtual machine can achieve near-native throughput. While this is a good result, it doesn’t tell the whole story. A shortcoming with most of these studies is that they use just a single 1 Gbps network interface card (NIC), which simply does not stress a modern system, virtualized or not. In an earlier paper, we addressed this by dedicating two NICs to a single VM and running an instance of netperf on each. This still was not a challenge. Now, in a Tech Note just published we used 3 NICs attached to a single UP Windows VM under ESX 3.0.1 and measured total throughput. This gives close to the maximum throughput possible in a fully-virtualized system. We compared this against native and the comparable configuration under XenEnterprise 3.2.0, the most recent version of XenEnterprise available. While both ESX 3.0.1 and XenEnterprise 3.2.0 yield near-native performance using one NIC, ESX gives considerably better performance with 2 or 3 NICs, demonstrating ESX’s lower overhead and better scalability.