Virtual Distributed Switch and vMotion

Hi,

I would be thankful if somebody can clear my doubts about this. We have an ESX 4.1 environment with 4 esx hosts. vmnetwork (vm port groups), management port groups, vmotion port groups and storage (nfs) all are on VSS in different vlans.

we recently got new 6 servers and will install esxi 5.1.0 on them. Then we will upgrade the existing vCenter server (which is currently on v 5.0) to 5.1. Then we will migrate vms from old hosts to new esxi 5.1 hosts.

We have to use Virtual distributed switches on new esxi 5.1 hosts.

My question is that should vmotion, management network and storage (nfs) port groups be on the VSS or VDS?

Should we only keep vm network (virtual machines) on VDS? if yes, why?

I would really appreciate your help in this.

Thanks.

AG