VMSnapshots

VMSnapshots refers to the capture of a virtual machine’s state at a specific point in time, including disk data, memory contents, and device status depending on configuration. Snapshots provide a way to preserve and restore a VM quickly, enabling rollback to the captured state without requiring a full restore from external backup media.

Common uses include testing and development, patch or configuration rollbacks, short-term backups before risky operations, and cloning base images. Implementations vary across hypervisors: VMware offers snapshots, Microsoft Hyper-V provides checkpoints, KVM/QEMU supports save/restore and qcow2-backed snapshots, and VirtualBox includes snapshot features. Snapshots may be full, differential/incremental, memory-including, or disk-only.

A key distinction is between application-consistent snapshots, which coordinate with guest software to flush in-memory state to disk, and crash-consistent snapshots, which capture the VM as if power were lost. Application consistency often requires guest agents or quiescing tools.

Limitations and operational considerations include increased storage usage as changes accumulate, potential performance degradation, and complexity when using long snapshot chains. Snapshots are not substitutes for regular backups or disaster recovery planning; they are intended for short-term state preservation. Best practices call for limiting snapshot lifetime and number, consolidating or deleting snapshots promptly, monitoring storage consumption, and testing restores to ensure reliability.