US Patent 7831560 Snapshot-aware secure delete

A snapshot-aware secure delete event identifying a file for snapshot-aware secure deletion on a computer system is received, and the file to be deleted is identified from the snapshot-aware secure delete event. Each file snapshot associated with the file on the computer system is accessed at the volume level and each non-duplicate file extent of the file snapshots is identified. The raw data identified by each non-duplicate file extent is securely overwritten using a secure overwrite technique, and each file snapshot is deleted from the computer system. In this way the raw data of the file and the raw data of all the diff areas of file snapshots associated with the file are securely overwritten and deleted.