Snapshots or checkpoints

Snapshots, called checkpoints in R2, are not commonly considered part of the high availability features of Hyper-V Server. However, they can be used to ensure and provide regular client access to services, so they fall within the scope. For the remainder of this section, only VHD files will be mentioned, although everything about snapshots also applies to VHDX files as well. Snapshot will be the term used, but remember that R2 uses the term checkpoint.

A snapshot captures the state of a virtual machine at an exact point in time. This includes its running processes, memory state, and even how its virtual hardware, such as virtual network adapters, is configured. Any VHD files that the virtual machines write to are frozen and new writes intended for those disk files will instead be placed in an AVHD file. The virtual machine continues to run uninterrupted. If necessary, you can revert to a snapshot. This stops the virtual machine, discards its current running state...