Increased Memory Usage on ESXi 4.1 from ESX 4.0

Hi All,

Recently we have migrated around 130 virtual machines from a ESX 4.0 U2 Cluster to esxi 4.1 u1 cluster and noticed the memory usage is much high on the hosts compared to 4.0.

The 4.0 u2 cluster had 255GB of RAM between 9 hosts and the new cluster has 355GB ram between 7 hosts.

4.0 u2 memory usage was around 60-70% and now on 4.1 they are on 90% usage. Can someone please explain this. Find it hard to understand that there is 100GB more RAM available on the new cluster but its using all of it.

ESX 4.0 u2 hosts were HP BL460 G1 - 32GB each

ESXi 4.1 u1 are HP BL460 G6 - 48GB each. 

Thanks