Perform differential backups as a supplement to full backups. Because they are usually faster and smaller, you can perform them more often than full database backups. They are also typically more efficient because they require less space on media and have a briefer impact on database performance than frequent, full database backups. Additionally, you can use them to minimize the number of Transaction logs you need to recover during a restore, because you would only need to restore those Transaction log backups performed since the differential backup.

 Differential backups are needed to performed when:

• A relatively small portion of the data in the database has changed since the last database backup. Differential database backups are most efficient if the same data is modified frequently
• You are using the Simple Recovery model, which does not permit Transaction log backups, and you want to perform backups more frequently than is practical for full database backups
• You are using the Full or Bulk-Logged Recovery model and want to minimize the time it takes to roll forward Transaction log backups when restoring a database

 Note: If a database is very active or a long time has passed since the last full backup, then a differential backup could take as long as a full backup.