Process for Upgrading from 4.1 Essentials Plus to 6.5 Standard?
Where I currently work is about to sign off on my request to get us properly licensed, and under maintenance, for vSphere and vCenter 6.5, where we currently operate a 2 host cluster with vCenter Server on Essentials Plus 4.1 (we also have a standalone 5.5 host on a free host license). The Std licensing will be for 6x CPU's and 1x vCenter, which will ultimately be used to repurpose existing hardware into a four host cluster using multiple existing HPE MSA SAN's and the vCenter Appliance.
One new host will be based upon new unused server hardware, so I'll have a clean slate on one hosts that will not immediately be running any production VM's.
Of course I can use all manner of documentation and peer discussion to formulate a plan for the upgrade, however I thought I'd also post this here to seek the advice of other users.
From what I'm aware of this is no simple task, I never thought it would be, however my main takeaway from everything is that this is going to have to be an iterative process moving up major versions at a time, e.g. 4.1 -> 5.0 -> 5.5 -> 6.0 -> 6.5?
I assume that all VMs are stored on the MSAs (i.e. on shared storage), and that the MSAs are supported by ESXi 6.5. I further assume that you are not using any 3rd party plugins (at least none which cannot be used on v6.5 anymore), and that your backup application - in case of VM based backup - also supports vSphere 6.5.
In this case I'd go ahead, and:
do a clean installation of ESXi 6.5, and vCenter Server 6.5
connect the host(s) to the MSAs
shutdown the VMs (one by one ) on the old hosts, remove them from the inventory, and register them on the new vCenter Server