@fabiorpn Basically you answered the question as to whether you do Maintenance on your hosts which you do. However updating a Host and rebooting it, it will render the VMs offline if not on HA. Assuming you do HA and that you move the VMs to the next host before reboot then you are good on that end. However my questions was geared more to the Security and Application Updates of the Severs (Be it Linux or Windows). When you install the updates and reboot it, essentially the VM is not accessible no matter how great your HA is. So that is where having a downtime/maintenance period is good even if you want to accomplish HA.