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Classification according to backup scale

Complete backup

A complete backup includes all data independent of the last change date. All data are saved and marked as saved data.

Incremental backup

An incremental backup include all data that changed after last backup. By using incremental backup Backup Window can be shortened, but RTO will be increased, because more steps are used for restore. During restore all data from the last complete backup and date from all incremental backups are used and recovered. Typically durin tape backup several tape sets are used for restorage.

  • adressed backup classification numbers:
    • minimization of Backup Window
    • disadvantage: raising of RTO (several tapes)
    • disadvantage: deterioriation of reliability (several tapes)

Differential backup

In case of differential backup all data modified since last backup (complete backup, incremental backup or differntial backup) are stored. The stored data volume can be minimized and so the Backup Window gets smaller. But RTO become bigger, because more restore steps could are necessary. In case of restore all complete and incremental backups are needed before differential backup to recover data.

In the typical sequence of weekly complete backup and daily incremental backup two tapes are used to recover data completely. Alternative solutions are technologies like CDP to get even better results.

  • adressed backup classification numbers:
    • minimization of Backup Window
    • disadvantage:raise of RTO (several tapes)
    • disadvantage deterioriation of reliability (several tapes)

Synthetic complete backups

The use of disk-based backup systems allowed elimination of disadvantages of differential and incremental backup. Systems, that support synthetic backups consolidate a complete backup with the following incremental or differntial backup to a new complete backup. Only this is used in case of dat restorage. This synthetic backup can be copied to tape without Backup Impact.

  • adressed backup classification numbers:
    • minimization of Backup Window
    • elimination of diadvantages of differntial and incremental backup