Different type of Data Back Ups.

There have been three basic types of backups: full, incremental and differential. More recently though, data backup software vendors have introduced some newer types of backups that you might not be familiar with.

Full backups

A full backup is exactly what the name implies. It is a full copy of your entire data set. Although full backups arguably provide the best protection, most organizations only use them on a periodic basis because they are time consuming, and often require a large number of tapes or disk.

Incremental backup

Drawbacks of full backups are so time consuming, incremental backups were introduced as a way of decreasing the amount of time that it takes to do a backup. Incremental backups only backup the data that has changed since the previous backup.

 Differential backups

A differential backup is similar to an incremental backup in that it starts with a full backup, and subsequent backups only contain data that has changed. The difference is that while an incremental backup only includes the data that has changed since the previous backup, a differential backup contains all of the data that has changed since the last full backup.
Suppose for example that you wanted to create a full backup on Monday and differential backups for the rest of the week. Tuesday's backup would contain all of the data that has changed since Monday. It would therefore be identical to an incremental backup at this point. On Wednesday, however, the differential backup would backup any data that had changed since Monday.
The advantage that differential backups have over incremental is shorter restore times. Restoring a differential backup never requires more than two tape sets. Incremental backups on the other hand, may require a great number of tape sets. Of course the tradeoff is that as time progresses, a differential backup tape can grow to contain much more data than an incremental backup tape.

Synthetic full backup

A synthetic full backup is a variation of an incremental backup. Like any other incremental backup, the actual backup process involves taking a full backup, followed by a series of incremental backups. But synthetic backups take things one step further.
What makes a synthetic backup different from an incremental backup is that the backup server actually produces full backups. It does this by combining the existing full backup with the data from the incremental backups. The end result is a full backup that is indistinguishable from a full backup that has been created in the traditional way.
As you can imagine, the primary advantage to synthetic full backups is greatly reduced restore times. Restoring a synthetic full backup doesn't require the backup operator to restore multiple tape sets as an incremental backup does. Synthetic full backups provide all of the advantages of a true full backup, but offer the decreased backup times and decrease bandwidth usage of an incremental backup.

Incremental-forever backup

Incremental-forever backups are often used by disk-to-disk-to-tape backup systems. The basic idea is that like an incremental backup, and incremental-forever backup begins by taking a full backup of the data set. After that point, only incremental backups are taken.