Snapshot backup tools like Azure Site Recovery and Veeam are great for sysadmins. They let you quickly replicate a virtual machine to somewhere else without knowing too much about the server’s contents.
To pull it off, they use the Windows Volume Shadow Copy Service to do snapshot backups – often referred to as VSS snaps. In a nutshell:
The VSS service tells SQL Server to freeze its writes SQL Server stops writing to each of its databases, freezing them SQL Server tells VSS, “Okay, I’m out” VSS creates a shadow copy of the data & log files VSS tells SQL