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Incremental and Differential Backups

Incremental and Differential Backups

With terabytes (or more) required to be backed up each day – it may not be feasible to perform a full backup. This is where incremental and differential backups are helpful. All companies require backups of their data. If not for the simple fact of being able to retrieve lost data; but also for many compliance based industries – it’s law.

In the end; the great debate is which is better? Incremental or Differential. Let’s shed some light on each.

Incremental and Differential Backups

What’s an incremental backup?

An incremental backup is a backup which captures only the changes since the last backup. This could either be a full backup, or another incremental backup.

In a ‘real life’ sense; a Full backup is run on a Sunday. Monday’s backup will then only copy what has changed since Sunday’s backup occurred. The same thing happens with each subsequent backup; until a new Full backup is run. Essentially each backup is just adding another link to the backup chain.  An incremental backup would can be graphically represented as such below:

A graphical representation of an incremental backup scheme.

A graphical representation of an incremental backup scheme.

The benefits of incremental backups are as follows:

  1. Fastest backup type as it copies the least amount of data each time.

  2. Reduced data being copied, means that more incremental backups can be stored on the same device compared to full or differential backups.

  3. Each incremental backup stores a different version of a file.

The drawbacks of an incremental based backup:

  1. To perform a successful recovery; you need the full backup and all incremental backups.

  2. If anything happens to any of the backups in the chain; then restoration may be impossible.

  3. While the backup side of things with incremental is particularly fast; the trade-off is that the restore process is particularly slow. This is mostly due to the requirement of the entire backup chain being required to restore files.

What’s a differential backup?

A differential backup is a backup which captures only the changes since the last full backup. This means that one differential file will contain all the changes that have occurred to the data set since the last full backup was performed.

Using an example similar to above; a full backup is performed on a Sunday. Then the Monday backup will contain all changes since Sunday. Now the difference between incremental and differential backups kicks in on Tuesday – which contains all the changes that happened since Sunday (just like the Monday backup did).

A graphical representation of an differential backup scheme.

A graphical representation of an differential backup scheme.

The benefits of differential backups are:

  1. Completes faster than a full backup does.

  2. Can fit more differential backups in the same amount of space compared to full backups.

  3. Only the full backup and one differential backup required to complete a restore successfully. This makes it more efficient than an incremental backup.

The downside of a differential backup:

  1. Larger backup window required when compared to incremental backups.

  2. More storage space required against incremental backups.

  3. Differential backups can grow quickly; especially without a regular full backup configured.

Selecting between incremental and differential backups

There is no right or wrong answer to this question. It all depends on what the business requirements and policies are around data protection. Such variables as RTO and RPO, backup window (how much time is allowed for a backup to run before it impacts day to day activities), even how much data you’re backing up can impact this.

When it comes to deciding between incremental and differential backups; it’s more likely that a combination of both will be end result. The reason for this is that they both counter each others deficiencies which gives an overall stronger backup strategy.

Need help to cut through the backup burden…

Are there not other things you could be doing for your business? Not completely sure on what to do in regards to business backup and recovery? Contact Test My Backups as we’re experts in this sort of thing. We’re able to configure an end to end backup solution for businesses of all sizes.

#backupmethods #differential #incremental

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