If you were to ask a person that was not familiar with computer backups, most would think that a backup was just an identical copy of all the data on the computer. In other words, if a backup was created Tuesday evening, and nothing changed on the computer all day Wednesday, the backup created Wednesday evening would be identical to the one created on Tuesday.
While it is possible to configure backups in this way, it is likely that you would not. To understand more about this, we must first understand the different types of backups that can be created. They are:
The type of backup that was discussed at the beginning of this section is known as a full backup. A full backup is a backup where every single file is written to the backup media. As noted above, if the data being backed up never changes, every full backup being created will be the same.
That similarity is due to the fact that a full backup does not check to see if a file has changed since the last backup; it blindly writes everything to the backup media whether it has been modified or not.
This is the reason why full backups are not done all the time -- every file is written to the backup media. This means that a great deal of backup media is used even if nothing has changed. Backing up 100 gigabytes of data each night when maybe 10 megabytes worth of data has changed is not a sound approach; that is why incremental backups were created.