There are quite a number of backup types and terms used when it comes to backups of your digital content. This is a compilation of the most common types of backup and backup strategy/policy with a brief explanation of their meaning, common examples, advantages and disadvantages.

Full Backup

      Full backup is a method of backup where all the files and folders selected for the backup will be backed up.  When subsequent backups are run, the entire list of files and will be backed up again. The advantage of this backup is restores are fast and easy as the complete list of files are stored each time. The disadvantage is that each backup run is time consuming as the entire list of files is copied again.  Also, full backups take up a lot more storage space when compared to incremental or differential backups.

Incremental backup

      Incremental backup is a backup of all changes made since the last backup. With incremental backups, one full backup is done first and subsequent backup runs are just the changes made since the last backup. The result is a much faster backup then a full backup for each backup run. Storage space used is much less than a full backup and less then with differential backups. Restores are slower than with a full backup and a differential backup.

Differential backup

      Differential backup is a backup of all changes made since the last full backup. With differential backups, one full backup is done first and subsequent backup runs are the changes made since the last full backup. The result is a much faster backup then a full backup for each backup run. Storage space used is much less than a full backup but more then with Incremental backups. Restores are slower than with a full backup but usually faster than with Incremental backups.

The Comparison of Backup Types:

                      

	Full Backup	Incremental Backup	Differential Backup
Backup Method	A backup of all files in a specified backup set or job	A backup of all changed and new files since   the last backup	A backup of all changed and new files since   the last full backup
Backup Speed	Slowest	Fastest	Faster
Restore Speed	Fastest	Slowest	Faster
Storage Needed	Most	Least	More
Advantages	- Fastest restore - Only needs the last full backup set to restore	- Faster backups - Less storage space used - No duplicate files	- Faster and simpler restores then   incremental backup - Only needs the first full backup and last differential   backup to restore
Disadvantages	- Needs the most storage space - Inefficient storage with a lots of   duplicates stored	- Slowest restores - - Needs all backup   sets full and all increments to restore	- Slower backups - Still stores a lot of duplicate files

Backup Strategy

      A backup strategy or backup policy is essentially a set of procedures that you prepare and implement to protect your important digital content from hard drive failures, virus attacks and other events or disasters.

Requirements for a good backup strategy

·         Able to recover from data loss in all circumstances like hard drive failure, virus attacks, theft, accidental deletes or data entry errors, sabotage, fire, flood, earth quakes and other natural disasters.

·         Able to recover to an earlier state if necessary like due to data entry errors or accidental deletes.

·         Able to recover as quickly as possible with minimum effort, cost and data loss.

·         Require minimum ongoing human interaction and maintenance after the initial setup. Hence able to run automated or semi-automated.

To plan your backup strategy

1. What To Backup

The first step in planning your backup strategy is identifying what needs to be backed up. Identify the files and folders that you cannot afford to lose? It involves going through your documents, databases, pictures, videos, music and program setup or installation files.

2. Where To Backup To

This is another fundamental consideration in your backup plan. In light of some content being irreplaceable, the backup strategy should protect against all events. Hence a good backup strategy should employ a combination of local and offsite backups.

Local backups are needed due to its lower cost allowing you to backup a huge amount of data. Local backups are also useful for its very fast restore speed allowing you to get back online in minimal time. Offsite backups are needed for its wider scope of protection from major disasters or catastrophes not covered by local backups.

3. When To Backup

Frequency: How often you backup your data is the next major consideration when planning your backup policy. Some folders are fairly static and do not need to be backed up very often. Other folders are frequently updated and should correspondingly have a higher backup frequency like once a day or more.

Backup Start Time: You would typically want to run your backups when there’s minimal usage on the computers. Backups may consume some computer resources that may affect performance. Also, files that are open or in use may not get backed up.

Scheduling backups to run after business hours is a good practice providing the computer is left on overnight. Backups will not normally run when the computer is in “sleep” or “hibernate mode”.  Some backup software will run immediately upon boot up if it missed a scheduled backup the previous night. Since servers are usually left running 24 hours, overnight backups for servers are a good choice.

4. Backup Types

Many backup software offer several backup types like Full Backup, Incremental Backup and Differential backup. Each backup type has its own advantages and disadvantages. Full backups are useful for projects, databases or small websites where many different files (text, pictures, videos etc.) are needed to make up the entire project and you may want to keep different versions of the project.

5. Compression and Encryption

As part of your backup plan, you also need to decide if you want to apply any compression to your backups.  For example, when backing up to an online service, you may want to apply compression to save on storage cost and upload bandwidth. You may also want to apply compression when backing up to storage devices with limited space like USB thumb drives.

If you are backing up very private or sensitive data to an offsite service, some backup tools and services also offer support for encryption. Encryption is a good way to protect your content should it fall into malicious hands.

6. Testing Your Backup

A backup is only worth doing if it can be restored when you need it most. It is advisable to periodically test your backup by attempting to restore it. Some backup utilities offer a validation option for your backups. While this is a welcome feature, it is still a good idea to test your backup with an actual restore once in a while.

Author: Roger