Running virtualized environment is so convenient that at times you may even forget that hardware on which all your VMs are running or Hyper-V host may need to be restarted… At this point reasonable question to ask is “What will happen with my VMs during host restart?” If we set aside clustered high-available Hyper-V implementations what actually will happen is defined on a per VM basis in VM properties (for stand-alone Hyper-V servers not participating in Hyper-V cluster or managed by SCVMM). Options which define this behavior on a per VM basis called “Automatic Stop Actions” and “Automatic Start Actions” respectively.
By default your running VM will save state & start automatically after reboot if they were started before Hyper-V restart. See screenshot of corresponding VM Settings section below.
As for other options you may configure in VM properties these are “Save the VM state (default)”, “Turn off the VM”, “Shut down the guest OS” (Automatic Stop Actions) and “Nothing”, “Automatically start if it was running when the service stopped”, “Always start this VM automatically” (Automatic Start Action). In Hyper-V v3 (part of Windows Server 2012) even more additional VM startup control options available to address “VM boot storms” and some other related issues (e.g. you may set startup memory allocation to be greater than memory allocated to VM when it up and running)…
As for logging you may find loads of Hyper-V related events under in Event Viewer > Applications and Services Logs > Microsoft > Windows. In particular when you shutdown your Hyper-V host event 14100 is recorded in Hyper-V-VMMS > Admin logs (“Shut down physical computer. Stopping/saving all virtual machines…”), and if you just Stopped VM Management Service via Stop button in Hyper-V management console then event 14090 is being registered in the same section (“Virtual Machine Management service is shutting down while some virtual machines begin running. All running virtual machines will remain running with no management access”).
And yes after you know that your second question naturally would be about conrolling VMs stop / start up order. There is no easy few click solution for this on stand-alone Hyper-V, but it’s doable. You may find one example of ordered VMs startup solution by John Savill on windowsitpro.com, and I believe you may find more options for that.