ESXi 4.1u1 host memory usage high vs ESX 3.5

[SystemAdmin01]

We recently reinstalled our ESX farm with ESXi 4.1u1 comming from ESX 3.5 (non i version).

When I now look at the memory usage percentage per host this percentage is much higher as before the migration. All the vm's have remained the same.

How is this possible?

[mittim12]

Welcome to the forums.  When you made the change from ESX 3.5 to vSphere 4.1 did you also change hardware?   What kind of hardware are you running on?  

[kjb007]

ESX 4.1 has support for Large  Memory Pages, so your memory utilization, at least from a host  perspective, will appear to be higher, but that is due to ESX using  large memory pages to support the guests.  This memory support is  dependent on "newer" processors that have extended page table/nested page table support.  This will typically show in larger apparent memory utilization at the host, and lower shared memory until there is more contention on the host for memory and those large pages are broken down to be shared.

-KjB

[SystemAdmin01]

Thanks for this explanation, but how can I then now see how much more systems I can host?  because the memory  usage seems much higher.

[kjb007]

This does make things a little more difficult for the admin.  If you want to get a ballpark of how much memory TPS could possibly save you, then you can take a look at the COWH counter for esxtop.

-KjB