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What is a Differential Backup


This help topic applies only to Backup4all. If you don't have it yet, you must download it first.

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Oct 14, 2022
Backup4all 9.x or older
You can read about the other types supported by Backup4all here: Backup types

What is a Differential Backup?

Differential Backup is a backup type that contains all the files that have been added or changed since the last Full Backup. The advantage of the Differential Backup is that it has a shorter backup time. However, if you perform the differential backup too many times, eventually the size of a backup archive might grow to be larger than the reference Full Backup archive.

Differential backup vs incremental backup

There is a significant distinction between the Differential Backup and the Incremental Backup types. Although they seem similar, their usage reveals the true difference.
The Differential backup only uses the last Full Backup as the reference for what to backup. Hence, it keeps accumulating the changes until another Full backup becomes the new reference.
In contrast, the Incremental Backup leaves out all changes that have already been backed up in one way or another. So, while the Incremental backup is more efficient in terms of space, the Differential Backup is more reliable as a backup source. The true versatility comes in combining the two methods to suit your needs.
Restoring a differential backup is a faster process than restoring an incremental backup because only two backup container files are needed: the latest full backup and the latest differential backup.
Backup4all uses the information it has recorded in its catalog file (".bkc") to determine whether a file has changed since the last full backup or not.
Use differential backup if you have a reasonable amount of time to perform backups. The upside is that only two backup container files are needed to perform a complete restore. The downside is if you run multiple differential backups after your full backup, you're probably including some files in each differential backup that were already included in earlier differential backups, but haven't been recently modified.

What are the advantages of differential backups?

  • Restore is faster than restoring from incremental backup
  • Backing up is faster than a full backup
  • It uses less storage space than full backup

What are the disadvantages of differential backups?

  • Restore is slower than restoring from full backup
  • Backing up is slower than incremental backup
  • It uses more storage space than incremental backup

Differential backup type in Backup4all

Backup4all supports the differential backup type and offers a solution for the slow backup issue.
differential backup
In time, the differential can grow to a size that is equal or larger than the full version. Therefore the following options can be used to trigger the creation of a new full backup:
  • Automatically make full backup if the differential exceeds...% of full backup size (default is 50%)
  • Automatically make full backup if the differential exceeds... (default is 100 MB)
The system calculates the backup size for the differential backup and if the selected condition is met it performs a full backup.