Thanks, Josh. I just added my vm layout to my signature, but in case it doesn't show up here - the 5424s are dedicated to iscsi and vmotion traffic with separate vlans for each. We enabled jumbo frames last year and saw a dramatic performance increase in backups and vmotion, but not much in the statistical jobs our users run that contain large data sets, so that's what I have my sights on now. Our processors support ept and each host has 284 GB ram, so we almost never see cpu or memory peg on the windows guests even during intense statistical jobs by multiple users. These are all through rdp and all apps are installed on the vm, so all processing is being done on the vm - no client processing.
Our Win2k8 R2 VMs have the e1000 vnics, which appear to set 9014 MTU without any way to adjust. The vswitches and host nics are set to 9000, but my understanding is that they allow for the header overhead. The 5424 is stuck at 9000 and does not allow for the overhead. vmkping tests top out at 8972 (since the header is added), so the switch has to be the bottleneck unless I'm wrong about the vswitch supporting the header.
Interested in more thoughts on the matter, especially if I'm off base on anything.
