Incremental Backup: What it is?

Incremental backup is a term used in a methodology of digital data backup. In an incremental backup framework, an initial backup is performed of “all” data selected for backup. Following the initial full backup, only data that has changed since the previous backup was performed is backed up. This means that there’s no need to spend resources (storage, bandwidth, etc.) backing up a fresh copy of all data in scope and the latest versions are still preserved for everything.

What is Incremental Backup?

Incremental backup is a backup method that only copies data that’s been created or modified since the previous backup. It is used when there is a large amount of data to be protected – only copying new or changed data saves time and storage space, making it a common method for online and cloud backup services.

How does it work?

An incremental backup scenario requires one full backup and then subsequent incremental backups over a period of time. For example, if a first full backup was performed on Monday, Tuesday’s incremental will take a snapshot and back up all new or changed files since Monday’s backup. However, Wednesday’s incremental will only back up files that have changed since Tuesday’s incremental backup and so on until another full backup is performed.

Because the initial full backup can take some time to complete, companies will often execute the full backup over a weekend when the data is less likely to be needed by the business.

To be able to restore up-to-date data or a full copy of the data, each of the incremental backups that were performed since the last full backup must be applied to that initial full backup. It can take some time to effectively reconstruct a new full backup to use for disaster recovery, but ostensibly the overall restoration process would still be faster and more efficient than trying to do full backups on a daily basis.

Why is incremental backup a good idea?

Incremental backups have two distinct advantages over a full backup.

• They complete much faster since the only files included are ones that have changed since the last backup.
• Impact on resources such as disk space and network bandwidth is minimized for the same reason.

A concept called deduplication is key to the ability to perform an incremental backup. Effectively many solutions will perform scans of files that have been changed to ascertain whether any of the data in scope already exists within the stored backup. Deduplication further increases backup speed and minimizes resource consumption – enabling backup software to check the backup repository for data it already has to avoid duplication of effort. You can either perform this deduplication at the file level, the block level, or both.

What types of incremental backups are there?

• Block level backup – this type will back up only the modified parts of the file, instead of backing up the entire file. It is useful for large files with few changes.
• Byte-level backup – this type is similar to block-level backup, but it is based on the binary variation of the file, compared to the previous backup. It uses the minimum unit to determine the part of the file to be backed up.
• Reverse incremental – The reverse incremental backup method produces a backup chain that consists of the last full backup file and a set of reverse incremental backup files preceding it. This way, the most recent restore point in the backup chain is always a full backup, and it gets updated after every successful backup job execution.
• Multilevel incremental – this is a more sophisticated incremental backup scheme that involves multiple numbered backup levels. A full backup is level 0. A level n backup will back up everything that has changed since the most recent level n-1 backup. Suppose for instance that a level 0 backup was taken on a Sunday. 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. If a level 2 backup was taken on Thursday, it would include all changes made since Monday because Monday was the most recent level n-1 backup.
• Incremental forever – this type is similar to the synthetic backup concept. After an initial full backup, only the incremental backups are sent to a centralized backup system. This server keeps track of all the increments and sends the proper data back to the client during restores.

Some disadvantages

There are some minor disadvantages to incremental backup it’s important to bear in mind:

• Slower restoration – The time saved in backing up the data gets added to the time needed to restore it. To give you a complete data set, you need to restore the last full backup, then each following incremental backup
• Possible incomplete restoration – In the unlikely event that any of the backups have failed, there is a chance you may not be able to recover all the data you need. A way of safeguarding against this is to arrange for an occasional differential backup to be done

Conclusion

Nowadays, it is common to communicate or work with others by using computers or mobile phones. Many precious data should be saved in case of a virus attack or the blue screen of death.

A piece of full information about incremental backup is offered on this page. Every backup method has its own features, and if you think it is necessary to back up your data with different methods, maybe a professional backup software can help.