I decided to write this post to remind you one important memory setting that has been changed in ESXi recently. I have been contacted by my customers about higher memory utilization of ESXi hosts after patching of VMware environment.
As it was mentioned some months ago at VMware site:
By forcing a flush and reload of cache memory, it is possible to measure memory timings to try and determine an AES encryption key in use on another virtual machine running on the same physical processor of the host server if Transparent Page Sharing is enabled between the two virtual machines. This technique works only in a highly controlled system configured in a non-standard way that VMware believes would not be recreated in a production environment.
Transparent Page Sharing (TPS) no longer allows inter-VM TPS by default:
- VMware ESXi 5.0 Patch ESXi500-201412401-BG Build 2312428
- VMware ESXi 5.1 Update 3 Build 2323236
- VMware ESXi 5.5, Patch 4 Build 2403361
and of course VMware ESXi 6.0.
To change a TPS behavior again, please follow an article here.
Note: Remember, if you are currently over-provisioning resources in your business critical applications cluster, you should review and re-evaluate your usage and consider adding resources to the vSphere Cluster or re-sizing your VMs. Because TPS is largely about memory, adding more memory to the ESXi hosts, or reducing memory allocated to the VMs, will be sufficient remediation. You should do it before doing any patching!