Very interesting Article on Jumbo frames. iSCSI and SAN are pretty fast already (in my experience) , but playing with MTU to gain even more throughput seems like a good idea. But is it really worth the effort? We would need to run speed tests before and after and fiddling with MTU could get a bit scary if not done correctly. I think our utilage is low anyway even with 2 1gb NICs (we havent switched on the 3rd NIC)
Anyway article here:
blog.scottlowe.org/2009/05/21/vmware-vsphere-vds-vmkernel-ports-and-jumbo-frames/
Make your own minds up.