Setup are 2 UCS blades in 2 datacenters 50 miles apart. However the backbone between the 2 is 40 Gigabits. The UCS's are connected with fiber at 10 gigs to a Cisco 3750 switch which is also 10 gigs. The San in one Datacenter is an EMC Isilon and the other datacenter used a Dell Equallogic. The 2 SAN's have a couple 1 gig connections. Here are my results.
A 3 gig file will copy between the 2 datacenters around a gig speed. That works from either a Virtual server's blade drives or from the Isilon which is NFS. Same with a physical Server 2008 on one of the blades that I built just for this testing. I would have thought that from one VM's own drives to the remote VM's own drives that I would get more than 1 gig speed.
On to a couple hundred thousand small files. Copying a test folder of 145,000 files that is about 100 gigs in size I get 10-12 MB's per second or about 1/10th of a gigabit connection. That happens between both datacenters and also from the Isilon's nfs share to the remote VM server (tested to the local VM's physical drive and also the SAN). Same results going from one VM server's physical drives to a Physical 2008 server in the other datacenter that I built for this testing.
It is just as slow (10 Mbs-copying that 100 gigs of data from the Isilon nfs share right to a VM's datastore which is also on the Isilon.)