File systems are backed up to make sure that if the data is lost by any hardware failure or any other issues, then, backup or dump can be used for restoring the necessary files in the system.
Incremental backup: In incremental backup, backups are taken periodically in a monthly, weekly or daily basis. The entire backup is not taken. Instead the backups are taken for only those files which have been changed after the last backup. Incremental backups are processed very quickly.
There are two methods used for backing up the disk to a tape memory: Physical backup and Logical backup.
Physical backup: A physical backup is a simple one where the entire disk block is copied to the tape from block 0 to block n. Advantage of physical backup is that it can be done in a very fast way.
Disadvantages of physical backup:
1) The main disadvantage of physical backup is that even the unused blocks are backed up in this process.
2) Physical backup takes the backup of entire disk and any directories cannot be skipped in the process.
3) Incremental backups cannot be taken.
4) Individual files cannot be restored.
Logical backup: A logical backup starts from a particular directory and backs up specified files and directories which have been changed after a set date. In logical backup individual files can be backed up and restored as per the requirements.