At a client site we came upon a problem with Windows 2003 VM’s. They would get low network performance when we moved them to a newly formed ESX cluster consisting of HP 460c G6 blades. In some cases logging on to the server with a remote session took about 20 minutes.
As I mentioned this only occurred when we moved a VM to the new cluster, but also VM’s that where newly installed would get the same problem when running on the new cluster. As we are using Altiris to install and configure new VM’s a colleague decided to install a new VM by going through the steps manually which normally would be done by Altiris and found out that after the activation of a security template the performance dropped significantly.