VM /ETC

Admins of heavily consolidated VMware VI 3 Clusters should make plans as soon as possible to download Update 5 of VMware vCenter Server to take advantage of increased performance and scalability. The latest update to vCenter 2.5 was released on July 10 and boasts improvements to support fail over management of up to 80 VMs per ESX/ESXi host in a HA (High Availability) Cluster.

The following details were taken from the VMware VirtualCenter 2.5 Update 5 Release Notes:

What’s New

Support for High Consolidation in VMware HA Clusters – VirtualCenter 2.5 Update 5 includes significant performance and scalability improvements to VMware HA. Use VirtualCenter 2.5 Update 5 for environments with more than 35 virtual machines (VMs) per host in an HA cluster.

For information on the ESX Server host settings required for this scalability improvement, see ESX Server host settings required for environments with up to 80 virtual machines per host in an HA Cluster (KB 1012002).

Upgrading or Migrating to VirtualCenter 2.5 Update 5

This release supports upgrading from VirtualCenter 1.4.1, VirtualCenter 2.0.2 (including Update 1, Update 2, Update 3, Update 4, and Update 5), VirtualCenter 2.5, VirtualCenter 2.5 Update 1, VirtualCenter 2.5 Update 2, VirtualCenter 2.5 Update 3, or VirtualCenter 2.5 Update 4, to VirtualCenter 2.5 Update 5. Review the detailed upgrade and migration instructions and guidelines that are provided in the Upgrade Guide.

Following the above link to KB 1012002 explains that upgrading vCenter 2.5 to U5 is just the start. VI 3 admins also need to make some additional configurations on ESX/ESXi hosts to achieve the 80 VMs per host improvements.

“Starting with the VirtualCenter 2.5 Update 5 release, an ESX Server host in an HA cluster can support up to 80 virtual machines. For all virtual machines to power on on other hosts in the cluster, if hosts within the failover capacity limit fail, you need to ensure that the following parameters in the ESX Server hosts are set with the following values:

Parameter	Value	Applicability
Misc.RunningVCpuLimit	192vCPU	ESX Server 3.5 and ESX Server 3i Embedded
Service console memory	512MB	ESX Server 3.5
vim resource pool memory reservation	1024MB	ESX Server 3i Embedded
Host agent memory configuration	<hostdStopMemInMB>380</hostdStopMemInMB> <hostdWarnMemInMB>300</hostdWarnMemInMB>	ESX Server 3.5 and ESX Server 3i Embedded

For specific instructions on setting each of these configurations on ESX/ESXi 3.5 hosts read KB 1012002.

It also appears that this KB offers some interesting tweaks for improving heavy VM consolidation on ESX/ESXi 3.5 hosts even if not managed by VC2.5 U5. Why would it not benefit admins to make these changes on hosts regardless of VI 3.5 Cluster membership?

Although not stated, I assume ESX Clusters with greater than 80 VMs per host should be upgraded to vSphere 4 in order to insure the best performance and scalability features.

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