We are upgrading from ESXi 3.5 to ESXi 4.1. What are the steps to update our server to 4.1? How do we migrate all virtual machines to the new server? We would also like to cluster the two servers once the migration is complete.
First, install ESXi 4.1 on the second server and make sure it can see the shared storage for the new cluster. Install the vCenter Server and create your new cluster. Once the cluster is created, add the ESXi server you just built, then add the 3.5 host. Mixed clusters are not a best practice, but this is only temporary.
Once you have both servers in the cluster and both can see the shared storage, migrate the servers from the 3.5 host onto the shared storage. Don't forget to set your Dynamic Resource Scheduler (DRS) mode to manual to avoid any accidents during this part. And remember, both machines must be able to see the vMotion network!
Once the machines are migrated onto the shared storage, put the 3.5 host into maintenance, then remove it from vCenter. At this point, rebuild the 3.5 host to 4.1 and add it to the cluster. You can re-enable full DRS automation at this point.
Last, your hardware versions and VMware tools will be out of date, so make sure to update tools on the guests, then upgrade the virtual hardware to take full advantage of the new features.
This was first published in September 2013