The host maintenance mode options can help you to reduce the downtime that's required to remediate an ESXi host by either choosing to power off or suspend the VMs running on it. Choosing to power off/suspend the VMs will cut down the time that would otherwise be required to VMotion the VMs off that host. However, keep in mind that we are gaining time at the expense of virtual machine downtime.

A host entering maintenance mode can fail at times. You can configure the number of retries vSphere Update Manager will attempt and the time interval between each retry. It is recommended that you choose to disable any removable devices connected to the VM, as this can prevent VMotion.