Snapshot software allows an administrator to make an instantaneous copy of any single virtual disk defined within the disk subsystem.

Snapshot software is available at different levels:

ESX/ESXi hosts allow you to create snapshots of virtual machines. This software is included in the basic ESX/ESXi package.

Third-party backup software might allow for more comprehensive backup procedures and might contain more sophisticated configuration options.

Administrators make snapshots for a variety of reasons:

Backup

Disaster recovery

Availability of multiple configurations, versions, or both

Forensics (looking at a snapshot to find the cause of problems while your system is running)

Data mining (looking at a copy of your data to reduce load on production systems)