In modern computing, there are three primary methods for archiving and backing up your data: full, differential, and incremental. The first method, a full backup, is pretty self-explanatory - it's copies all of the data from one drive or system to another. While this does result in a complete backup, this method is often long and, most importantly, it's unnecessary in most cases. Instead, most modern users will utilize differential or incremental for their regular data backup needs.
What are Differential Disk Images?
The differential disk image is the final product of a differential data backup. In this scenario, a full backup is created when the first system backup is performed. After that, each subsequent backup only copies the data that has changed since the last full backup. Not only does this reduce the amount of time it ultimately takes to complete each backup, but it also reduces long-term wear and tear on your hardware.
In a disaster recovery scenario, restoring data from a differential backup usually result in the least amount of downtime when compared to other methods. This is largely dependent on the lifespan of the backup itself, however, as differential backups tend to grow over size. As a result, the amount of time that it takes to make the backup - and the amount of time required to recover the data - increases, too.
Depending on the amount of data that has changed, differential backups can be rather time consuming. Although they offer more versatility than full backups, most modern users prefer incremental backups over any other method.
What are Incremental Disk Images?
Much like a differential disk image, an incremental disk image is the result of an incremental data backup. When the first incremental backup is made, a full backup is created - this is true with all three backup methods described. However, subsequent incremental backups will only copy the data that has changes since the last backup - be it a full backup or an incremental backup. It's faster than full and differential backups, but it does have its own drawbacks to consider.
The majority of the disadvantages associated with incremental backups are actually encountered during the data recovery and restoration phase. Because the backup needs to recall the original (full backup) as well as the incremental changes that have been made since the original backup was made, some datasets can take a long time to process.
Another potential drawback is the requirement that all files must be present within the image set. If one of the incremental images are missing, either due to accidental deletion, data corruption, or something else entirely, the resulting backup will not be usable when attempting a data recovery.
Which Method is Right for You?
Finding the ideal backup method for you or your organization really comes down to your exact needs, your budget, and the importance of the data you're backing up. While a full backup ensures that a complete, recent copy of your data is always available, it's certainly not the easiest or most efficient method out there. While differential and incremental backups also have their benefits, they also have some disadvantages to consider, too.