Unable to enter maintenance mode - ESXi 6.0

[Panicinprogress]

Hello and Happy Holidays to everyone,

I am having issue with one of our ESXi servers - cannot put it into maintenance mode to do upgrade from 6.0 to 6.5. Process just freezes at 75% for hours. I do have 2 VMs (powered off) on that host which I cannot vMotion to other hosts - both of them have physical connections to tape drives which other 2 ESXi servers don't have. 

Can this be the reason why it is not kicking in maintenance mode? 

[lhedrick]

If the VMs are powered off...

Try to enter Maintenance Mode again but this time clear the check box that says Move powered-off and suspended virtual machines to other hosts in the cluster.

You may be right that the VMs are being passed through to some physical hardware on the host.

[Panicinprogress]

I don't have that checkmark when I try to put in the maintenance mode. 

It just says this:

When in maintenance mode, VMs cannot be created, powered on nor configured. 

Additionally, VMware vCenter Server will not migrate any to this host while it is in maintenance mode. 

You might need to either power off or migrate the virtual machines from the host manually.

You can cancel The Enter Maintenance mode task at any time. 

Are you sure you want to put this host in maintenance mode?

Yes/Cancel

[e_espinel]

Hello.
whenever you work with upgrades, you should always have a full backup of all VMs and the ESXi host configuration, in case something goes wrong.

Your case is strange, it could be that version 6.0 is not patched or even worse it is the base image (without any patch).
A quicker way would be to boot the host with an ISO image of version 6.5 and choose the option to upgrade ESXi, preserve VMFS datastores.

Remember that if you have vCenter Server you should upgrade it first and then the ESXi Host.

Another way would be to patch version 6.0 to the latest available level, and then try again to upgrade to version 6.5.