[UPS] preferred behavior in case of a power failure

I'm running several different OSes types on a single machine an like to suspend
them in case of a power failure. Since many of them can not be shutdown with
'qm shutdown <vmid>' or take to long to shutdown themselves I need to put
them on "hold". All VMs are using the local LVM storage.

Is it possible to suspend all VMs and save their state/memory to disk?

What is the preferred way to handle a power failure shutdown?

Lars