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Incremental vs Differential Backup Explained

User at a media company with 51-200 employees

There are many types of backup used to both guard and recover data in cases where data integrity is compromised. Data can change very fast, slowly, or not all. Data can be very sensitive or common. Because data can change hourly, daily, or weekly and be of differing importances, a data backup process that aligns with the needs and resources of the business should be selected.

We’ve reviewed the capabilities of the best backup software to understand the main differences between incremental and differential backup, which are the two most common types. Both are extensions of a full backup process, which as its name implies, is a complete copy of all digital assets.

Incremental backup

An incremental backup is a copy of whatever data has changed since the last backup. Thus, if you perform a full backup of your system on Sunday, an incremental backup on Monday will only copy and store any data that has been changed or added since Sunday. An incremental backup on Tuesday will only deal with data that’s changed since the Monday incremental backup, and so on.

Incremental Backup Process

An incremental backup process can be very fast, less than an hour, and the storage capacity needed will be quite small in comparison to a differential backup or full backup. If the full backup was 50 gigabytes, the incremental changes from one day to the next might be 1 gigabyte. The backup manager will have to decide how often to do incremental backups. It might be daily or weekly, or even hourly. That depends on how much change is occurring in the data and how critical it is for continued business operations. If there’s any concern about network capacity or storage, an incremental backup process is most the best choice.

Recovery time for an incremental backup process can be lengthier in comparison to a differential process. Since there are more backups created during an incremental process, each backup logging changes from the last backup, it takes time to piece everything back together. So, the benefit of the quick backup time is offset by a longer recovery time.

Overall, incremental backups are good for organizations that need flexibility and short time periods between backups. Compared to differential backups, an incremental backup copies less information. The “backup window” is shorter. The files are smaller. If your business needs consistently high network performance, you might prefer incremental backups to differential backups, as they typically make lighter demands on the network.

Differential backup

A differential backup is comparable to an incremental backup, in that it’s a backup extension of a full backup. However, unlike an incremental backup, the differential backup backs up the data that has changed since the last full backup. Thus, if you do a full backup on Sunday, a differential backup on Monday will back up all the data that’s changed since Sunday. Then, on Tuesday, the differential backup will also back up everything that’s changed since Sunday. The Wednesday and Thursday differential backups will similarly back up everything that’s changed since the full backup on Sunday.

As you can see, the differential backup process is longer, recording changes in the data since the last full backup, which creates a more resource intensive process requiring larger storage capacity. If you have limited resources or need a faster backup time, an incremental approach may be a better option.

The recovery time using a differential process is much faster in comparison to an incremental process. Since it backs up data changes since the last full backup, there is only one large backup as opposed to the multiple of incremental. Recovering data from one large block in addition to the full backup is much faster than recovering and piecing together multiple blocks.

If your business needs a fast, simple way to restore lost data, a differential backup may be a better option than an incremental backup. A sacrifice in backup up speed and storage capacity will need to be given, but the recovery process will be fast.

Full backup

The term “full backup” is actually a little bit misleading. Hypothetically, the full backup involves backing up all elements of a data asset. However, this is not always true. If the asset in question is a single file or data object, then yes, a full backup will be a complete, unique copy of the asset. However, if the digital asset is a system of some kind, like a website, operating system or database server, the full backup typically does not include every single system file, library and supporting configuration file. That is done in what is known as a “day one backup.”

The “day one backup” truly has everything in it. As it contains everything, it takes a long time to backup. However, it takes the least amount of time to restore since it’s only one large file and nothing needs to be pieced together.

Differential vs Incremental Backup vs Full Backup

Type of Backup




Full backup

Backs up all elements of a data asset (except for underlying system files, which are backed up in the “day one backup.”)

It’s complete, so it offers a single file to restore.

Rapidly becomes out of date and requires a lot of storage.

Incremental backup

Backs up all data that has changed since the last backup, e.g., since the last full backup or the last incremental backup.

It’s the most up-to-date backup.

Fastest backup.

Small backup files; low network and storage requirements.

Data recovery can be time-consuming and more challenging.

Differential backup

Backs up all data that has changed since the last full backup.

Fast data recovery time.

Requires longer backup times and more storage capacity.

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reviewer1766661 - PeerSpot reviewerreviewer1766661 ( IT Architect - AI at CGI)
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There are also techniques that can perform progressive incremental forever (always incremental backups).

That type of backup can be done on the object level, where an object can be a file or block.

IBM Spectrum Protect has been using these techniques since its first release.

With spictera brick solution, one can take application-consistent snapshots and store these snapshots using progressive block-level incremental forever backup techniques.

- The more often one takes a backup, the less amount of data to send.

The restore is also faster as only one backup copy is needed to restore the data. Instead of restoring full, and all of its incremental changes, it has already a view of how the system looks at that particular point in time.

With spictera brick which uses IBM Spectrum Protect, the snapshot volumes are re-animated internally on the OS and presented as a snapshot volume on the server, where a "merge back" can be started immediately in the background.

This makes the restore time to be nearly instantly.

One can compare this ideology with how an OS "lvconvert --merge -b" works on a Linux system.

The benefit of this technique is that it uses much less resources both during backup, but also during restores.

And especially if one wants to restore only a portion of a system, then one does not have to wait for the restore to finish before collecting the data of interest.

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