1) Install the latest vCenter from VMware.
The best release is the latest release, vCenter 4.1, and it has shown superior performance over earlier releases. If you are still using vCenter v2.5, be sure to install the latest level, Update 6 (build 227637). The early update levels of vCenter v2.5 will not work with the agent, and VMware currently supports only Update 6.2) Install the latest VMware VI agent.
If you haven't already, install the new v6.2.3, available since February, 2011. Details are here:3) Set Validate SSL Certificates to No.
VMware Agent v6.2.3 Details
If you are still running v6.2.2, upgrade to v6.2.3 or the latest Interim Fix, which fixes a number of APARs:
VMware VI Interim Fixes
When configuring the agent, most users want to communicate via SSL, but getting the right certificate can be a challenge. Most users set "Use SSL Connection to Data Source" to Yes, but set "Validate SSL Certificates" to No. The data still uses SSL, but certificates are ignored.4) Install Microsoft hotfix on Windows 2003 SP2.
If you run the agent on the same Windows 2003 SP2 machine as the vCenter, you may need a Microsoft hotfix to avoid TCP problems. Go here to find out more:5) Increase the heap size for large environments.
TCP Hotfix Information
You might need to increase the java heap size for the agent's data provider if you have a large VMware environment, such as more than 100 ESX hosts and more than 1000 virtual machines. For details, see the User's Guide (the recommendation applies to v6.2.2 and v6.2.3):Still having a problem with the VMware VI agent? Look at this section on the support wiki on how to search the logs for information that might help:
Setting Java Heap for VMware VI Agent
VMware VI Agent Common Tracing
And you can always contact IBM Support - we'll be glad to help!