Creating checkpoints

In Hyper-V, a checkpoint is a captured image of the state, data, and hardware configuration of a VM at a particular moment in time. Creating checkpoints is a convenient way for administrators to revert a VM to a previous state at will. For example, if you create a checkpoint just before applying a system update, and the update is somehow problematic, you can apply the checkpoint and return the VM to the state in which it was before you applied the update.
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Prior to Windows Server 2012 R2, the checkpoints in Hyper-V were known as snapshots. Checkpoints function in exactly the same way as snapshots; only the name is changed. You can expect to see either term on the 70-410 exam.
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Creating a checkpoint is as simple as selecting a running VM in Hyper-V Manager and selecting Checkpoint from the Actions pane. The system creates a checkpoint file with an AVHD or AVHDX extension, in the same folder as the VHD file, and adds the checkpoint to the Hyper-V Manager display, as shown in Figure 3-20.

FIGURE 3-20 A checkpoint in Hyper-V Manager

Checkpoints are a useful tool for administrators implementing a test environment in Hyper-V, but they are not recommended for heavy use in production environments. In addition to consuming disk space, the presence of checkpoints can reduce the overall performance of a VM’s disk subsystem. Administrators also should not use checkpoints on VMs containing databases—such as those created by SQL Server, Exchange, or Windows domain controllers—because the checkpointing process does not account for the current state of the
database, and corruption might occur.