Comparison and Discussion of Backup Types

Certain backup strategies may work better depending on the how often and intense the data to be backed up is being modified. Single backup operations can be divided into full backup, differential and incremental backups. Differential and incremental backup require at least one full backup to take place initially. BackupChain supports regular data file and directories (folder) backups and there is also the possibility to back up only certain file formats. In addition, entire disks and partitions may be backed up and saved as image. In all cases, it is possible to restore only parts from a full computer backup set using Granular Restore technology.

Full Backup

Full backup is what most users consider a regular backup. Files are locked (a complete drive, a partition, certain directories or specific files, certain file formats) and copied to backup media. Files may be compressed and deduplicated, depending on the user’s preferences.

Disk Image Backup

Image backups involve the entire disk (usually the hard drive, but also USB mass storage,  Hyper-V virtual disk backups, optical media and also disks on the local network) or just a partition through a 1-to-1 image. Image backups back up not only files but also entire file systems, including the operating system and user settings. The advantage of this protection method is that in the case of a total hardware failure of the computer the system may be fully restored to the way it was when last backed up. When restoring entire file systems their original structure is restored with all properties and settings.

There are also programs on the market that can also incrementally create such backups for several years using deduplication.

Differential Backup

Differential backups are backups that store all the data files that have changed or were added since the last full backup.

Incremental Backup

Incremental backups store only files that have changed since the last backup cycle. This technique uses storage space more efficiently but has the disadvantage that when restoring all backups need to be read and restored. This strategy is particularly useful for Hyper-V and other virtualization platforms, such as VMware and VirtualBox.

Detect Modified Files

To distinguish changed files and already backed up unmodified files, some file systems employ special file attributes that change automatically, for example, the archive bit on FAT and NTFS.

Towers of Hanoi

To achieve a good compromise on the number of stored backups and the hardware available, one can use the “Towers of Hanoi” backup type. This backup strategy is based on the eponymous puzzle game. Each backup media used is equivalent to a slice of the towers and a backup on the appropriate media is used at every movement of the disc. Thus, the first medium is used every other day (1, 3, 5, 7, 9, etc), the second every fourth (1, 2, 6, 10, etc) and the third every eighth (4, 12, 20, etc.).

Using N media you may need 2 ^n-1 days until the last medium is overwritten.

The following tables show which media are used and on which days. It must be noted that this method overwrites the first backup after only two days.

Towers of Hanoi Using Three Media:

Towers of Hanoi for four media

Towers of Hanoi for five media

The following is a list of backup software publishers:

Sources

Wikipedia and company websites