Hi Tim,
That sucks having to check such a huge environment. I only have 2 hosts running about 15 VM's, so it was easy for me to check all our mahcines.
I had checked this before and all of my VM's are set with no reservations or limits imposed on their memory usage.
This really has me stumped as on some machines the difference between what the OS and what vSphere think the machine is using can be up to 500mb. This is causing me some concerns when it comes to right sizing my environment as I don;t know which metric to trust when deciding how much memory to allocate to my VM's.