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Backup Strategy

Incremental vs. Differential Backup: What Is the Difference?

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What Is Incremental Backup?

What Is Differential Backup?

Incremental backup involves creating copies of recently modified data. Instead of creating a full backup that copies an entire dataset, an incremental backup process copies only the data modified since the last incremental backup.

Incremental backups can help increase backup speed while decreasing the overall storage space your backups consume. However, it can increase recovery time because the backup system might need to combine multiple incremental copies to restore a user’s data.

Differential backup involves taking an initial full backup copy, and then backing up all data modified since the last full copy. A full backup is taken periodically (for example, once per week) to ensure data integrity.

Differential backup takes longer, compared to incremental backup, but makes recovery easier by requiring only the initial full copy and the latest differential backup.

This is part of our series of articles about backup strategy.

In this article:

What Is a Full Backup?

A full backup process creates at least one copy of all data files you wish to capture within a single backup operation. Typically, data protection specialists or backup administrators determine in advance which files to duplicate during a full backup process.

Here are the common data types you can copy during a full backup operation:

  • Files your applications need to use.
  • Metadata that makes these files useful to your applications.
  • Tracking files and logs that document what your applications are processing.
  • Any other needed control and management files.

Here is what you do not usually copy during a full backup operation:

  • Applications
  • Operating systems
  • Any other software

You can capture these components for disaster recovery using other techniques like disk cloning or disk mirroring.

Related content: Read our guide to backup strategy

Incremental Backup vs. Differential Backup: Pros and Cons

Incremental Backup Pros and Cons

The primary advantage of incremental backups is that you don’t need to copy as much data as with differential backups. Incremental backups also require less storage space and shorter backup windows—between full backups.

The disadvantage of incremental backups is that it can be time-consuming to restore data. For example, with a daily backup policy, if you wanted to restore the backup data from Tuesday, you would first restore Sunday’s full backup, then Monday’s backup. Only then could you restore Tuesday’s data.

Furthermore, if any backup media is damaged or missing, your data recovery will be incomplete.

Related content: Read our guide to incremental backup

Differential Backup Pros and Cons

The advantage that differential backup has over incremental backup is a shorter restore time. When speed is critical, such as in a disaster recovery situation where downtime can’t be tolerated, quick restores are essential.

Restoring a differential backup never requires more than two copies of the dataset: the initial full copy and a differential backup. Comparatively, incremental backups could demand a large number of backup sets.

The main drawback is that the differential backup size grows every time you create a new backup—until the next full backup. This process can increase backup window duration and affect the amount of storage space required to retain the differentials.

Incremental Backup vs. Differential Backup: Key Differences

Here are some aspects to consider when choosing a backup.

Backup Speed

Typically, a full backup is considered to be slowest, incremental backup is the fastest, and differential falls in between. While this speed assessment is the rule, there are exceptions. If, for instance, you have newly changed or added files containing more data than the original files, then incremental and differential backup processes are slower.

Once you’ve created the first full backup, differential and incremental backups take the same amount of time, assuming you add a few new files but don’t delete any other files. In most cases, however, incremental backup is faster than differential backup, which is faster than a full backup.  

Storage Space

Differential backup generally requires more storage space than incremental backup because it stores more data in the form of image files, requiring more space for image files. The difference in the backup size is usually larger if the backup schedule is longer.

Costs

Initially, full backups require the most storage space, while differential backups require more space than incremental backups. However, the increments increase as the data sets change and grow over time, with each backup potentially taking up more storage space than a regular full backup.

Restoration

Regardless of the type of backup you restore, you need to have at least one full backup. In addition, to perform a full backup you will need:

  • For differential backup- the most recent differential backup copy
  • For incremental backup- every incremental backup made from the time of the full backup until the point of recovery

Since restoring from a differential backup requires fewer steps than using incremental backup, it lets you restore from backup faster. Restoring from incremental backup is slower, and also depends on having multiple backup copies - if any of them are missing, restoration can fail.

However, if you only need a partial restoration of recently created data, incremental backups are the preferred choice. Another advantage of incremental backups is that they are faster than full backups and require less storage space.

Cloud Backup

Incremental backups are typically more suited to the cloud than differential backups because they don’t consume as many resources. Incremental backups require less storage space, which translates to lower storage costs in the cloud.

Incremental and Differential Backup with NetApp Cloud Backup

NetApp understands ONTAP better than anyone else, which is why the best backup solution for ONTAP systems is NetApp Cloud Backup. Designed by NetApp specifically for ONTAP, Cloud Backup automatically creates block-level incremental forever backups. These copies are stored in object format and preserve all ONTAP’s storage efficiencies. Your backups are 100X faster to create, easy to restore, and much more reliable than with any other solution.

Cloud Backup simplifies the entire backup process. It’s intuitive, quick to deploy, and managed from the same console as the rest of the NetApp cloud ecosystem.  Whether you’re looking for a less expensive way to store your backups, a faster, more capable technology than NDMP, or an easy way to enable a 3-2-1 strategy, Cloud Backup offers the best backup solution for ONTAP.

Learn more about NetApp Native Backup in the Cloud, Designed for ONTAP, and find out more in our Cloud Backup Service Customers’ Case Studies.

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Semion Mazor, Product Marketing Manager

Product Marketing Manager