Playing around with Virtual Server 2005, I ran into some very slow guest OS’s – some reacted very, very slowly, so here’s a hint:
If you are experiencing that one or a few of your guest OS’s are slow but the others are running as expected, you probably have starved the slow ones. Give them more RAM to speed things up. The easy way to check whether a guest is starved is to compare the assigned RAM to the Commit Level (Task Manager) and at the same time look at the page fault delta values (Task Manager, Processes tab, select columns). If you want to get the most out of your RAM, you probably will run with the Commit Level some above the amount of RAM – but too much paging will slow you down.