Virtual device interface (VDI) reference

Applies to: yesSQL Server (all supported versions)

This section contains the specifications for SQL Server application programming interfaces intended for use by third-party backup software vendors.


The virtual device interface (VDI) provides the highest online backup throughput with minimal degradation to the transaction workload, as well as the fastest possible restore times. It enables third party vendors to achieve the same performance characteristics as the SQL Server native backup/restore, and makes the full range of backup/restore functionality available. VDI was introduced in SQL Server 7.0 and is supported and enhanced in later versions.

VDI supports two primary types of backup technologies:

  • Conventional online backups where the entire contents of the backup set is read and transferred to the backup media.

  • Snapshot backups using underlying split-mirror or copy-on-write technology.

Conventional online backups done through VDI can take advantage of the full range of features of backup and restore in SQL Server. Snapshot backups are limited to full database and file/filegroup backups only. However, snapshot backups may be rolled forward with conventional database differential, file differential, and transaction log backups.

Next steps

Review the VDI reference documentation in this section.

Download the full specification and the supporting source files:

SQL Server 2005 Virtual Backup Device Interface (VDI) Specification