Hi,
Currently we have 4 ESXi hosts with HA/DRS and running on ESXi 4.1 and VCenetr server Standard 4.0. We are planning the upgrade to version 5.1. And the license we have is VMware vSphere 4 Enterprise Plus, also have valid support contract with VMware.
1. Are we able to upgrade the hosts to ESXi 5.1 while VM's are online or required any downtime?
2. Is there any cost involved in the upgradation?
3. How to upgrade from ESXi 4.1 to Esxi 5.1
I would appreciate any feedback on this.