Types of Backup Explained


Discussions about backup tend to dive straight into the technical aspects of creating safe copies of vital data. They may miss what is arguably a more important issue, which is the purpose of the backup process itself. When looking at explanations of the different types of backup available to IT managers, it’s worth keeping in mind that backup and restore processes ideally serve business objectives - ensuring business continuity, recovering from disasters like cyberattacks, and enabling operational technology to remain in service with as little interruption as possible.

In reviewing the offerings of the best backup software, we’ve put together options that should keep these higher level objectives in mind, help you create a sound backup strategy, and leverage all the advantages of data backup and recovery.. There are four main approaches to backup: full backup, incremental backup, differential backup, the mirror backup. There is no best type of backup. There is only the method that works best for a particular organization’s needs. That said, the fastest backup and restore process is generally the best, all things considered.

Jump to our Comparison Table for Types of Backup.


Full backups

What is full data backup?

A full backup involves making a copy of an entire digital asset, such as a database or data set. It’s the most basic and rudimentary backup type. Typically, whoever is in charge of backups will conduct a full backup of a file on a periodic basis.

However, its name notwithstanding, in the case of a system backup, a full backup typically does not replicate every single little piece of the system. That is the job of the “Day Zero” backup, which occurs right after a system has been successfully installed and configured. A “Day Zero” backup makes a 100% complete copy of every system file for safe keeping, including files and libraries. These files don’t change very often, so it’s not worth wasting time and resources backing them up as regularly as a full backup process.

Advantage

There’s minimal time needed to restore the data. Since everything is backed up at one time and it’s a copy in its entirety, everything can be restored at one time as well.

Disadvantage

A full backup can take up a lot of storage space and a lot of time to backup. It’s storing and recovering the full data set, which can be quite large, as opposed to storing and recovering the portion of the data set that has changed.


Incremental backups

What is an incremental backup?

An incremental backup copies only that data which has changed since the last full backup and since the last incremental backup. An incremental backup process is particularly useful when dealing with transactional databases, which are constantly changing. When it’s not practical to make a full backup because of resource constraints (i.e. time or storage) or the pace at which data assets change, an incremental approach is more pragmatic.

So, imagine that there is a full backup performed on Sundays. (Weekends are a good time to do an operation with such high network and system load.) On Monday, an incremental backup would only replicate anything that changed in the period between Sunday and Monday. If the incremental backup schedule is daily, then the Tuesday backup would copy any data that changed since Monday, and so forth.

Advantage

Very little storage space is required when executing an incremental backup process since only data that has changed will need to be backed up. It’s also a very fast process given the limited amount of data in comparison to a full backup.

Disadvantage

Restoration is the slowest in comparison. All incremental changes in addition to the full backup need to be reconciled to accurately restore the data, which takes more time than a full or differential backup process. Additionally, if one incremental backup record in the chain is “broken”, it can jeopardize the latter incremental backups.


Differential backups

What is a differential backup?

A differential backup is similar to an incremental backup, with one important difference. Every time a differential process is executed, it backs up all data that has been modified or generated since the last full backup and ignores previous differential backup instances. An incremental backup process only backs up data changes since the last incremental backup was run.

For example, if the full backup was on Sunday, and there is a differential backup done each subsequent day of the week, then Monday’s differential backup will copy data that’s changed since Sunday. The differential backup on Tuesday will copy all the data that’s changed since Sunday, as will the differential backups on Wednesday, Thursday, Friday and Saturday.

Advantage

The recovery process for a differential approach is much faster than an incremental approach since there is only one differential backup block versus the multiple contained in the incremental approach.

Disadvantage

Differential backups require more storage space and more time to backup than an incremental approach.


Mirror backups

A mirror backup is a backup that makes an exact copy of the source data. The advantage of this approach is that it does not store any old or obsolete data. This advantage can cause a problem, though, if files get deleted by accident. Then, they are permanently lost. The mirror backup approach is often used in highly critical systems, such as financial and stock trading platforms where a nearly instant restore of extremely recent data is needed to meet recovery time objectives (RTOs) and recovery point objectives (RPOs).


Backup Types Comparison Table

Backup type

Definition

Benefits

Drawbacks

Full backup

A complete copy of the source data.

Comprehensive and easy to restore.

Takes a lot of time and system resources—cannot be done frequently.

Incremental backup

Copies data that has changed since the last backup, either full or incremental.

Is efficient in use of network and system resources. Can be performed frequently.

Can be complicated to restore.

Differential backup

Copies data that has been changed since the last full backup.

Relatively fast and easy to restore.

Takes longer and uses more system resources than an incremental backup.

Mirror backup

Creates an exact copy of source data.

Enables nearly instant, complete restoration of lost data.

Can result in accidental permanent loss of data.

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