Microsoft® SQL Server™ supports backing up or restoring individual files or file groups within a database. This is a relatively sophisticated backup and restore process usually reserved for very large databases (VLDB) with high availability requirements. If the window of time for backups is not long enough to support backing up the full database, then subsets of the database can be backed up at different times. For example, if it takes three hours to back up a database, and backups can be performed only during a two-hour window each day, and then half the files or file groups can be backed up on one night and half the next.
If a disk holding database files or filegroups fails, the site can restore just the lost files or filegroups. They must also be making transaction log backups, and must restore all transaction log backups made after the file or filegroup backup.
File and filegroup restores can also be made from a full database backup set. This allows for a quicker recovery because only the damaged files or filegroups are restored in the first step, not the entire database.
Using File or Filegroup Backups