Incremental Backup

An incremental backup is a copy of the backed-up data than contains only new or changed data relatively to the last backup session. When you perform incremental backup for the first time, Veeam Agent for IBM AIX creates a full copy of your machine data that you selected for backup. During subsequent backup sessions, Veeam Agent for IBM AIX copies only new or changed data and saves this data to a separate backup file in the same backup location.

Incremental backup may be useful if you want to regularly back up your data. It allows you to keep multiple copies of your data related to a specific point in time in the same backup location without consuming additional disk space in the backup location.

To create an incremental backup, you must configure backup settings, and then start the incremental backup process. You can perform these tasks with the Veeam Backup Console or using the Veeam Agent for IBM AIX command-line interface.

Incremental backups typically take less time than full backup. Veeam Agent for IBM AIX copies the whole amount of data only during the first backup session. During subsequent backup sessions, Veeam Agent for IBM AIX copies only changes, not the whole amount of data.

How Incremental Backup Works

To create incremental backups, Veeam Agent for IBM AIX uses the GNU tar utility. Veeam Agent uses this utility to track data that changes on disk between two incremental backup sessions, copy the backed-up data and store it to a backup file. During the data recovery process, Veeam Agent for IBM AIX also uses the GNU tar utility to retrieve the backed-up data from an incremental backup.

The GNU tar utility is included in the Veeam Agent for IBM AIX installation and operated as a part of the product. The utility is located in the /opt/veeam/cd directory on the machine where you installed the product. The utility is also included in the recovery image, allowing you to perform bare-metal recovery of your machine from an incremental backup.

During incremental backup, Veeam Agent for IBM AIX creates and maintains the following types of backup files:

• .tar.gz — a compressed archive file that stores the backed-up data. Veeam Agent for IBM AIX creates such files during every incremental backup session.
• .snar — a snapshot file that contains backup metadata — information about files that were backed-up within the latest incremental backup session. Veeam Agent for IBM AIX creates one snapshot file per backup chain at the time when the first backup file in the backup chain is created. During subsequent backup sessions, Veeam Agent updates the snapshot file.

Every incremental backup session produces a new backup file in the target location. Backup files make up a backup chain. To learn more, see Backup Chain.

Veeam Agent for IBM AIX performs incremental backup in the following way:

1. When you start the incremental backup process for the first time, Veeam Agent for IBM AIX reads the whole amount of data that you selected for backup, copies it to the target location and stores it to the backup file of the .tar.gz format. The name for the first backup file in the backup chain is machine.tar.gz.
2. Along with the backup file, Veeam Agent for IBM AIX creates in the backup location the machine.snar snapshot file. The snapshot file contains information about files that were backed up within the current backup session.
3. During the next incremental backup session, Veeam Agent for IBM AIX checks whether files listed in the snapshot file were changed, added or removed since the previous backup session. Veeam Agent for IBM AIX copies only new or changed files to the target location and stores them to the backup file with the machine.tar.gz.0 name.
4. During subsequent incremental backup sessions, Veeam Agent for IBM AIX repeats operations performed at the step 3. For each backup session, Veeam Agent creates a new backup file: machine.tar.gz.1, machine.tar.gz.2, and so on.
5. After the number of files in the backup chain exceeds the number of backup files to keep, Veeam Agent for IBM AIX transforms the backup chain. To learn more, see Backup Retention Policy.

Related Tasks

• Performing Backup
• Performing Backup with Command-Line Interface