BACKUP TYPES

Backing-up is a crucial process that everyone should do in order to have a fail-safe, for when the inevitable happens. The principle is to make copies of particular data in order to use those copies for restoring the information if a failure occurrs (a data loss event due to deletion, corruption, theft, viruses etc.).

You can perform the backup manually by copying the data to a different location, or automatically using a backup program.

Each program has its own approach in executing the backup, but there are four common backup typesimplemented and generally used in most of these programs: full backup, differential backup, incremental backup and mirror backup. A type of backup actually defines how data is copied from source to destination and lays the grounds of a data repository model (how the back-up is stored and structured).

The image below provides an overview comparison between these backup types

Full backup

Full backup is the starting point for all other backups and contains all the data in the folders and files that are selected to be backed up. Because the full backup stores all files and folders, frequent full backups result in faster and simpler restore operations. Remember that when you choose other backup types, restore jobs may take longer.

It would be ideal to make full backups all the time, because they are the most comprehensive and are self-contained. However, the amount of time it takes to run full backups often prevents us from using this backup type. Full backups are often restricted to a weekly or monthly schedule, although the increasing speed and capacity of backup media is making overnight full backups a more realistic proposition.

Full backups offer the best solution in data protection and given that you can schedule a backup to run automatically, it requires little intervention compared to the benefits. A single full backup provides the ability to completely restore all backed-up files and folders, as exemplified in the image below:

However, you should be aware of a significant security issue: each full backup contains an entire copy of the data. If the backup media were to be illegally accessed, stolen or lost, the entire copy of your data could be in the hands of unauthorized persons. This is why when deciding to use a backup program to make full backups, make sure it supports encryption to protect the backed-up data.

Advantages:

1. Restore is the fastest
2. The entire backed-up data is stored in a single file (better storage management)

Disadvantages:

1. Backing up is the slowest compared to other backup types
2. The storage space requirements are the highest (compared to incremental backup or differential backup). Considering how cheap storage devices are now, this is a low impact disadvantage.

As a recommendation, even if full backup offers the most protection, it's good to have a backup strategy in place where full backups are performed weekly, and faster backup types (such as incremental) are executed daily. 

Incremental backup

Incremental backup stores all files changed since the last FULL, DIFFERENTIAL OR INCREMENTAL backup. The advantage of an incremental backup is that it takes the least time to finish. The disadvantage is that during a restore operation, each increment is processed and this could result in a lengthy restore job.

Incremental backup provides a faster method of backing up data than repeatedly running full backups. During an incremental backup, only files changed since the most recent backup are included. That is where it gets its name: each backup is an increment for a previous backup.

The representation below shows how a backup job running four times would look like when using incremental:

The time it takes to execute the backup may be a fraction of the time it takes to perform a full backup. Backup4all is a backup program that supports incremental backup, and it uses the information recorded in its catalog file (.bkc) to determine whether each file has changed since the most recent backup.

The advantage of lower backup times comes with a price: increased restore time. When restoring from incremental backup, you need the most recent full backup as well as EVERY incremental backup you've made since the last full backup.

For example, let's assume you did a full backup on Friday and incremental backups on Monday, Tuesday and Wednesday. If you need to restore your backup on Thursday morning, you would need all four backup container files: Friday's full backup plus the incremental backup for Monday, Tuesday and Wednesday. By comparison, if you had run differential backup on Monday, Tuesday and Wednesday, then to restore on Thursday morning you would have needed only Friday's full backup plus Wednesday's differential.

Advantages of incremental backups:

1. It is the fastest backup type since it only backs-up increments
2. Saves storage space compared to other types
3. Each backup increment can store a different version for a file/folder

Disadvantages for this backup type:

1. Full restore is slow compared to other backup types (you need the first full backup and all increments since then)
2. To restore the latest version of an individual file the increment that contains it must be found first.