From a reliability perspective, today's Windows servers far surpass the Windows servers of yore. However, even the reliable server requires the occasional reboot for patches and, in rare cases these days, servers might even blue screen and require a reboot. During a reboot, virtual machines are unavailable and once the server comes back up, default behavior calls for all virtual machines that were running prior to the reboot event to come back up.
To configure a virtual machine's startup settings, use the Hyper-V Manager to open the properties page for that virtual machine and choose the Automatic Start Action option as shown in the figure below.
Figure 1: Here's a look at the configuration screen for a Hyper-V-based virtual machine that starts automatically if it was running when its host either crashed or was rebooted
Here are the options that you have at your disposal:
- Nothing. Do nothing. You will need to manually restart this virtual machine if the host crashed or is rebooted.
- Automatically start if it was running when the services stopped. Any virtual machines that were running prior to reboot will be automatically returned to a running state once the host reboots.
- Always start this virtual machine automatically. Regardless of the state of the virtual machine prior to the reboot, bring this virtual machine into operation after any reboot.
- Startup delay. If you have 20 virtual machines all booting at the same time, you could suffer from serious resource contention (a boot storm) that makes if tough to bring all of the machines back into operation in a timely manner. To avoid this, stagger boot times by delaying the startup of virtual machines. You need to configure this setting on a per-VM basis.