A couple of weeks ago the VMware Performance Team released a new interesting paper about a virtual deployment of Microsoft Exchange Server 2007 on vSphere 4.0 Release Candidate (build 140815).
The 16,000 mailboxes environment was distributed across 8 virtual machines (Windows Server 2003 R2, 14GB RAM, 2 vCPUs, 20GB vHD and 2000 users each) served by a HP ProLiant DL 580 G5 server with 4 Quad-Core Intel Xeon X7350 @ 2.93GHz and 128GB RAM.
The backend storage was served by a NetApp FAS6030 array with 114 disks split into four aggregates (the data on was made of 40 disks).
VMware tested the same environment with Microsoft Exchange Load Generator (8-hours workday simulation) using a 4GB Fibre Channel connection, a 1GbE iSCSI connection and a 1GbE NFS connection.
Despite this major difference in the available bandwidth the three protocols performance are very similar: