Methods to upgrade & migrate to esxi5.0
There are over all three methods to upgrade to ESXi5.0. There are listed below
1. Perform a scripted upgrade
You can upgrade or migrate hosts from version 4.x ESXi and ESX to ESXi 5.0 by invoking an update script, for an efficient, unattended upgrade. Scripted upgrades provide an efficient way to deploy multiple hosts. You can use a script to upgrade ESXi from a CD, DVD or USB flash drive, or by PXE-booting the installer. You can also call a script from an interactive installation.
2. Upgrade or migrate interactively using an ESXi installer ISO image on CD/DVD or USB flash drive
You can run the ESXi 5.0 installer from a CD/DVD or USB flash drive to do an interactive upgrade or migration.The installer works the same as for a fresh installation, but if you select a target disk that already contains an ESX/ESXi 4.x installation, the installer upgrades the host to 5.0, and gives you the option to migrate some existing host settings and configuration files, and preserve the existing VMFS datastores.
3. vSphere Update Manager (VUM)
If your site uses vCenter Server, VMware recommends that you use Update Manager. vSphere Update Manager is software for upgrading, migrating, updating, and patching clustered hosts, virtual machines, and guest operating systems. Update Manager orchestrates host and virtual machine upgrades..
from ESX4.0(classic) & ESXi4.x to ESXi5.0
from ESXi5.0 to ESXi5.xVUM