Iâ€™m a big fan of simple vSphere network configurations, one vSwitch with a small number of fast uplinks. This has been my stance since ESX 3 and I think itâ€™s still a good starting point for a network design. I have had some concerns about the vNetwork Distributed switch (vDS) with itâ€™s management through vCentre and the inherent ability to make a mistake that break the vDS for every ESXi server that uses the vDS. In the past I couldnâ€™t be unreserved about my suggestion that there be a single vDS as the whole network configuration for group of ESXi servers as the ability to break a lot of hosts with one mistake is a big risk. An example would be changing the VLAN ID of the VMkernel portgroup (used to connect to vCentre) to the wrong value, rendering every ESXi server unmanageable with a single error. With great power comes great responsibility. Combine this with the difficulty of managing the vDS from the ESXi shell made me more confortable with a hybrid environment, a vNetwork Standard Switch (vSS) for the management VMkernel portgroup and a vDS for all VM and IP storage traffic. Recovering a broken vSS from the ESXi command line is a pretty well documented process of esxcfg-vswitch and esxcfg-vmknic commands.
With the release of vSphere 5.1 the vDS acquired an awesome new ability, the ability to automatically back out a toxic change. If a vDS configuration change on a host removes the ability of that host to connect to vCentre then the change is undone on the host. This removes my objection to putting the management VMkernel port on a vDS and makes me happy with a return to my one vSwitch policy even when that one switch is a vDS. With the huge manageability benefits of vDS this makes me very happy.
From what Iâ€™ve read any vDS change that results in the ESXi server being unable to talk to vCentre for 20 seconds is automatically undone. So far I havenâ€™t been able to test the rollback by making toxic changes on purpose, as soon as I get the vSphere 5.1 AutoLab build that Grant Orchard has put together tested I plan on some serious wreckage to make sure this works how it sounds.