Hello, we have license and support vCenter Server 5 Essentials and wanted to know if the upgrade to 6.0 of the ESXi is free or only updates in version 5.5. Additionally, can you inform me if to carry out these updates, you must do with the host in maintenance mode or is it possible to do them live?
As long as you have a valid support contract (which you do), you can upgrade your licences with no additional cost. You can proceed to https://my.vmware.com to do that. Find your licences under "Manage License Keys" section and you can upgrade them there.
License key requirements for new version of VMware products