What is a incremental backup?
A incremental backup is a backup of every file on a filesystem which has been modified since the last backup.
An incremental backup is the fastest backup and requires the least storage space on the backup media. However, incremental backups also require the longest time and the most tapes to restore.
Incremental backups should be used only in environments where backup time or backup storage media are severely constrained. For most environments, a weekly full backup and a daily differential backip represent a better plan.
If you perform a full backup on Saturday along with incremental backups every night and the system crashes on Wednesday, you will need to restore the full backup from Saturday along with the incremental backups from Sunday, Monday, and Tuesday.
In contrast, if you perform a full backup on Saturday and a differential every night, when the system crashes on Wednesday you will only need to restore the full backup from Saturday and the differential backup from Tuesday.