You can look at it this way:
The vCenter piece of the Distributed Virtual Switch is for consistent management across datacenters. You could loosely imagine it as the supervisor module in a physical chassis-based switch.
But the actual virtual switching is done at the ESX host. vCenter will create a hidden standard vSwitch on each host attached to the dvSwitch. In a way, this is like a line card in a physical chassis-based switch.
If vCenter dies (physical, virtual, whatever), the virtual switching plane on each of the hosts remains intact and functional.
My physical analogies aren't completely perfect, I admit, but I think they help with the visualization of the solution.
-jk
