Bare metal restore

A bare metal restore is the process of reformatting a computer from scratch after a catastrophic failure. Typically the process involves reinstalling the operating system and software applications and then, if possible, restoring data and settings. 

Volume Shadow Copy Service (VSS)

VSS is a set of Component Object Model (COM) application programming interfaces (APIs) that provides standardized interfaces, enabling third-party backup and restoration software to centrally manage the backup and restore operations on a variety of applications. VSS also implements a framework that enables volume backups to be performed while applications on a system continue to write to the volumes.

VSS has three components:

• Requestor—The application that requests the creation of a shadow copy. 
• Provider—The interface that provides the functionality to actually make the shadow copy. 
• Writer—Application-specific software that acts to ensure that application data is ready for shadow copy creation.  

Requestors, providers, and writers communicate in the VSS framework to create and restore volume shadow copies. A shadow copy of a volume duplicates all the data held on that volume at one well-defined instant in time.

A requestor initiates the backup and restore processes. The provider controls the processes and instructs a writer to prepare a dataset for backup. When everything is ready, a requestor then instructs a provider to create a shadow copy.