We began in inititive to reconfigure all our ESX hosts to utilize the round robin access policy for all our SAN datastores as a way to improve throughput. I originally wrote a powershell script using PowerCLI to go from host to host (by host or by cluster) and reconfigure all detected LUNs with the round robin policy. The unfortuante problem with this method was any LUN added after this was completed would have to be changed manually as well.
After attending a troubleshooting class the esxcli command was brough to my attention, after some further investigation I found it was recently integrated into PowerCLI (v332441). With this information I decided to write a PowerCLI script to reconfigure all my hosts (either by host or by cluster) to use round robin by default. All our arrays are active/active arrays, using the SATP VMW_SATP_DEFAULT_AA, my script is configured to change this specific SATP.
To use this cmdlet you must have the PowerCLI build 332441, which was released in December of 2010. The script prompts for input several times but only prompts once for username/password for the hosts.
I have only run this script against ESXi 4.1, please do you own testing and verification if you decide to make use of this PowerCLI script.
