Virtio on infiniband HW expected performance?

Hi all
we are evaluating the purchase of infiniband hardware together with Nehalem-based servers, for KVM use.

What performance can we roughly expect with virtio-net over infiniband hardware?

Communication would be primarily for these 2 purposes:

1- VM to a HN: primarily NFSv4 imports from the fileserver (a HN) to the VMs, for the files shared by multiple VMs. 2- HN to HN: fileserver serving VM disk-images via NFSv4 to the HN which is running KVM.

What performances can I roughly expect in these 2 cases? Also, for evaluating case #2: what is the performance of virtio-blk?

Our VMs would be 70% linux, 30% windows.

Thank you
Asdo