If you use the general ESXi 7.0 ISO, you might have issues with VIBs installed by your previous ESXi version. You should also know that if your hardware is server hardware of a particular vendor, there might be a particular ESXi ISO to download because this ISO will contain the vendor’s VIBs and drivers needed by your hardware.

In this case, you have to shut down VCSA and all the other VMs running on a particular host, and then do a manual upgrade. The alternative is a manual upgrade of ESXi. vSphere Lifecycle Manager (vLM) is a preferred tool, but for smaller environments you need alternatives.

You can also be in a situation where you are running just vSphere Essentials Kit, which does not have the vMotion license, so you cannot use vSphere Lifecycle Manager (previously vSphere Update manager) to update your host where VCSA is running because you cannot put the host into the maintenance mode. If you don’t have vCenter and are still running a couple of ESXi hosts, which are not managed by vCenter server appliance (VCSA), you still need to upgrade ESXi to the latest version.