Hi Alistar,
Thanks for your suggestions. I agree with you but the contractor thinks it's not a good idea since DVS depends on vCenter Server; when vCenter Server goes down, we can't manage the networks/switches, see the comment below. I think the benefits of VDS outweigh the risk not be able to make changes to the network when vCenter Server is down. Your thoughts?
"I read the Memo and recommendations for moving Management and vMotion to a Distributed Virtual Switch, but I do not agree with it. If vCenter goes down, data will continue to traverse the switch, but you will be unable to manage those switches directly from the host. If you needed to do any modifications to those networks/switches for troubleshooting you would not be able to. "