When databases grow too large to be backed up all at once, filegroups can provide an alternative backup method. Filegroups can be backed up at different times and frequencies. Filegroups that change often can be backed up more frequently than filegroups that remain more static. In certain situations, filegroup backups can greatly reduce restore time. For example, if a nonprimary filegroup is destroyed or corrupted, only that filegroup has to be restored.

Backup Exec includes two methods for backing up filegroups: full and differential. The full method backs up the entire filegroup. The differential method backs up only the changes made to the filegroup since the last full backup. A differential backup is smaller and faster than a full backup, so differential backups can be run more often than full backups. Consider using differential backups when only a relatively small amount of data changes between full filegroup backups, or if the same data changes often.

Because differential backups allow the restore of a system only to the point that the differential backup was created, you should also create multiple log backups between the differential backups. Using transaction log backups enables you to recover the filegroup to the exact point of failure. A combination of full and differential filegroup backups and transaction log backups provides complete database protection. Log backups are required to be able to recover a system from a filegroup backup.