With the release of VMware ESX/ESXi 3.5 and VirtualCenter 2.5 U3 VMware implemented a few interesting changes in it’s Availability implementation.  In this document VMware HA and the latest changes are described in detail.

This document is intended for experienced HA cluster admins who are planning to migrate to Update 3 as well as admins who are interested in the explanation of some cluster essentials.

A sample from the High Availability document:

The release notes for ESX / ESXi 3.5U2 VCU2 mention “DNS Resolution Is No Longer a Requirement to Enable VMware High Availability on ESX Server Hosts”.

That means, that ESX servers do not rely upon any DNS settings and/or even the host file /etc/host to resolve the DNS names of the other cluster members.

When the new host joins an HA cluster, the VirtualCenter server provides it with the IP address of one of the HA cluster members, which initially gives the host the network information it needs to contact one of the cluster members.  That one cluster member then supplies the network information for all other nodes in the cluster after initially contacted. This information is stored into the FT_HOSTS file located in

  • /etc/opt/vmware/aam/FT_HOSTS on standard ESX
  • /var/run/vmware/aam/FT_HOSTS    on ESXi