1. Introduction: Backup Terminology

Nowadays you'll find many backup methods, options, and features in the wide range of backup software products available in the marketplace. These products let you choose from among simple to complex backup options. To make the most of your backups and to choose the solution that's right for you, you need a working knowledge of applicable terminology. So, that's where we'll start.

Here's some basic terminology that's widely used to describe backup solutions:

On and Offline Backups Online Backup: for notebook PCs, this means the drive on to which backups are made or from which a recovery will be done is active. The drive may be in use, or it may be idle and waiting for user interaction and it may be directly attached to the notebook or available on a network, but the drive is online and working when a backup is made or a recovery needs to be done. Offline Backup: Offline backups are those where the backup image or file set is stored on a medium, such as a tape or disk cartridge, that must first be located and mounted before it can be used.

Another consideration in the online-offline arena is whether your notebook is online or offline. Because they are designed to move around, there will be times when your notebook is not able to reach your local backup environment, whether an external disk drive, a tape drive or another computer on your home or office network. We'll talk about this situation later.

Types of Backups Full Backup: an archive comprised of all files on a system, usually including system state, registry data, and other information necessary to restore a notebook completely; not just files by themselves, but everything that a properly configured system needs to operate. Incremental Backup: an archive comprised of all files that were modified since the last backup was made, whether it was a full or incremental backup. Differential Backup: an archive comprised of all files that have changed since the last full backup. Selective Backup: an archive composed of only some files on a computer, for example all Word and Excel files.

Because each incremental backup includes only files that changed since the last backup, when recovering a large number of files or a complete disk drive from a full backup and related daily incremental backups, it might be necessary to first restore from the last full backup and then restore all or most of the incremental backups in order. Most commercial backup software deals automatically with this situation.

Because the latest differential backup has all of the files that have changed since the last full backup, recovering many files or an entire disk is less complex than with incremental backups. The full backup and the latest differential backup are all that is needed to fully or partially restore a disk drive.

Incremental backups save storage space on your backup medium because they contain only what has changed since the last backup, not everything that has changed since the last full backup as with differential backups.

Selective backups can be made using full, differential and incremental backup types. Of course, with selective backups, any backup is really a partial backup. Selective backups are often done manually using specialized software (e.g. Super Flexible File Synchronizer) or commands such as copy and xcopy, which are available at the Command Prompt in Windows. Batch files can be used to more or less automate Command Prompt based selective backups.

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