Updating esx 3i
You can upgrade or migrate hosts ESX/ESXi 4.x to ESXi 5.0 by invoking an update script.
To view a guide, click one of the following links: All the documentation for ESX Server 3.5 Update 2 applies to ESX Server 3.5 Update 3 as well.
Note: Update Manager 5.x does not support upgrading ESX hosts to a later version of ESX (ESX 4.0 to ESX 4.1).
It only supports upgrading from ESX/ESXi 4.x to ESXi 5.0.
You can run the ESXi 5.5 installer from a CD/DVD or USB flash drive to do an interactive upgrade or migration.
This method is appropriate for deployments with a small number of hosts.