A Unix example would be: The use of rsync's --link-dest option is what makes this command an example of incremental backup.
A level 1 backup taken on Monday would include only changes made since Sunday.
A level 2 backup taken on Tuesday would include only changes made since Monday.
A level 3 backup taken on Wednesday would include only changes made since Tuesday.
An incremental backup of the changes made between two instances of a mirror can be forward or reverse.
The main advantage of this type of backup is a more efficient recovery process, since the most recent version of the data (which is the most frequently restored version) is a (synthetic) full backup, and no incrementals need to be applied to it during its restoration.
This server keeps track of all the increments and sends the proper data back to the client during restores.
If enough disk space is available, an online mirror can be maintained along with previous incremental changes so that the current or older versions of the systems being backed up can be restored.
At the moment, these are the technologies that achieve the highest relative compression of the data, turning into a great advantage for the security copies carried out through the Internet.
As only the incremental backups read data from the disk, these are the only files that need to be transferred during offsite replication.
The overall consumed I/O is the same as the reversed incremental, but during the duration of the backup activity only 1 write I/O is used and the snapshot of the VM is opened for less time than the reversed incremental; the remaining 2 I/O are used to update the full backup file.