How third-party SQL Server backup tools access databases' files for backup?

I'm reading about Red Gate SQL Backup, and I liked the concept of creating a database backup compressed and writing on disk the compressed backup directly without a开发者_运维百科n intermediate SQL Server native backup.

And I'm wondering how this type of software make backups. It accesses the database files directly? It uses some sort of SQL Server or Windows API? Windows Shadow Copy?

The SQL Server has an API for backup providers to plug in elements into he backup pipeline. See INFORMATIONAL: SHEDDING LIGHT on VSS & VDI Backups in SQL Server, or have a look at the SQL Server Compressed Backup project on sourceforge.

More information at:

• A Guide for SQL Server Backup Application Vendors
• SQL Server 2005 Virtual Backup Device Interface (VDI) Specification

It uses the "SQL Server Virtual Device Interface (VDI)" as per the Datasheet.

You can't shadow copy or use a Windows API to backup SQL server files

CodeProject VDI wrapper if you want to write your own