What is Differential Backup? Definition and Comparison

What is a differential backup?

Differential backup is one method of backing up data, which involves backing up files, folders, and hard drives. It starts with a full backup, so differential backups rely on a full backup. It copies all the data and files that have changed since the last full backup.

To better understand the differences between differential, full, and incremental backups, watch this 3-minute video.

There are four key moments to watch for.

• 00:24 Two important backup rules
• 00:42 An example to explain the difference
• 02:01 Characteristics of full, incremental, and differential backups
• 02:44 How to create a better backup strategy

Why did you choose differential backup?

After a full backup, data changes every day or week, and disk space does not permit a full backup daily. That is why we need incremental backups. If it is impractical to back up all your data every day, then it is unlikely that you have so much change in your data on a daily basis.

Differential backups can be very helpful. When you need to restore your data, you would use the full backup and the latest differential backup to do so.

What does differential backup mean? A differential backup is a type of backup process where only the files or data that have changed since the last full backup are backed up. Unlike a full backup, which backs up all files, a differential backup focuses on the alterations made since the previous full backup. This approach saves time and storage space while still offering a level of data recovery capability. When restoring data, the latest full backup is first applied, followed by all the changes recorded in the differential backups, bringing the system back to its state at the time of the backups.

For example, if a full backup runs on Monday, the backup that runs on Tuesday backs up all files added since the full backup on Monday.

Monday: Create a full backup that contains 10 files. Tuesday: Add two files and perform an incremental backup. You'll get two new image files. Wednesday: Add three more files and perform another incremental backup. You'll get the two image files added on Tuesday and the three newly added image files.

Comparison of Full Backup and Differential Backup

A full backup is a copy of all data and files. It's a well-known backup solution, widely covered in articles, and the easiest to understand.

These take longer to create and use more space on your computer, but are ideal for infrequent, full backups, such as once a month.

Differential backups rely on full backups, because they record changes made since the last full backup. Because they copy less data than a full backup, you can create differential backups more frequently. However, differential backups still have a drawback: as backup cycles lengthen, differential backups become more like full backups.

Incremental Backup versus Differential Backup

Incremental and differential backups can be confusing because they both copy changed data. An incremental backup, however, copies data that has changed since the last backup – which could be a full backup, a differential backup, or an incremental backup.

It's best to back up small amounts of data at a time. Incremental backups take up less space and don't take too long to create. However, restoring all your data from incremental backups is complicated. If one file is corrupt, you may not be able to recover all your data.

If you perform a full backup on Sunday, the incremental backup on Monday contains only data changed since Sunday. The backup on Tuesday contains only data changed since the last incremental backup (which was on Monday). Differential backups address some of the problems with incremental backups, reducing the likelihood of file corruption and making it easier to restore files than with incrementals.

Advantages and Disadvantages of Differential Backup

Differential backups are an excellent way to back up changed data, but they're not perfect. Here are some pros and cons of differential backups:

Advantages:

• Like incremental backups, differential backups don't require backing up as much data or files as a full backup.
• A differential backup doesn't take much time to complete, making it a time-saving backup method.
• Differential backups are relatively easy to restore. However, you still need the previous full backup to perform a differential backup.

Disadvantages:

• Not as secure as a full backup.
• Files can become corrupted during a differential backup.
• While a differential backup takes less time than a full backup, restoring a full backup is quicker than restoring a differential backup.
• Differential backup files can grow quite large over time and may even exceed the size of the original full backup.

Conclusions

Each method has its quirks. It is hard to say which is “better,” since they all have their uses in certain circumstances.

This article explains the pros and cons of differential backups, along with the reasons to opt for or against them. If you're a business user, a single backup approach might not cut it for your needs.

Use differential, incremental, and full backups to ensure data safety.