By David Fox

Anyone coming into contact with the subject of data backup may come across the term ‘incremental’ in relation to backups.

You may not understand what it means, or even worse, have a partial understanding.

In this article, we’ll fill in the gaps by explaining a few concepts around the backing up of data and associated terms.

What is an Incremental Backup?

A backup is a repeating process of making a copy of a set of files and folders. The purpose of this practice is to be able to recover (or restore) in them event of a loss or failure. An incremental backup is simply saving only those files that have changed since the last time a backup was made.

For example, take the ‘documents’ folder on a computer, where you might be storing some work. If you were to attach an external hard disk to your computer and make a copy of this folder, you now have a backup. Unplug the external disk and put it somewhere safe. 

The following day, you modify some of the documents on your computer, and you create a couple of new ones. Your backup is now out of date. To update it, you’ll need to re-attach that external disk. You now have two choices:

  1. You take a ‘Full Backup’ by copying the entire documents folder to your external disk. You rename the previous backup folder so that you now have two full copies of the documents folder. One from yesterday and another from today. For a small folder, this is a simple and effective backup strategy.
  2. You take an ‘Incremental Backup’ by figuring out which files have changed and which were added. Then, copy those to your backup disk so that your backup is up to date again.

The incremental backup technique is more efficient than full backup since only changed files need to be saved again. Likewise, manually figuring out what has changed is time-consuming and prone to mistakes. Therefore backup software is usually used to automate this task.

How Incremental Backup software works

Generally, backup software includes the following features:

  • Scheduling of full or incremental backups at convenient times.
  • Retention of data over time, and recycling of oldest data out of the backup
  • Volumes—the splitting of backed up data into container files that can reside on disks or tapes or within cloud storage. Backed up files are stored inside the containers.
  • Compression and encryption of data to save storage space and add security
  • Keeping track of everything that’s been backed up, so it can be located again later and restored/recovered.

When using backup software to perform incremental backups, changes since the previous backup are detected. The software does this by comparing the previous backed up with the current files and folders on the disk. This may include inspection of the names of files, file sizes, modification dates, and various other attributes stored with the files on the computer.

It is possible to keep performing incremental backups over long periods. However, when restoring data from the backup, having to go back to the very first full backup and then combine all the incremental backup steps to reproduce what was on the computer at a given point in time can become complex. A database is generally used to keep track of which files and folders existed on the computer at a given point in time.


Conclusion

Incremental backups are an important part of understanding how backup software works and nearly all backup software employs some form of this technique to efficiently keep a security copy of data. Archiware P5 Backup is a sophisticated backup software product that uses Incremental backups to achieve a point-in-time restore. It incorporates all the features listed above, and maintains a database that serves both to keep track of everything that has been saved and where it’s stored and also as an easy way to identify and select files for restore.

What is an Incremental Backup? Definition and How It Works