Backup types

A full backup of a client, also known as a master backup, captures all data selected for protection. For file-level backups, you can use selection lists to exclude unwanted data, and for Windows clients, you can also specify which files to include. For applications and virtual machine infrastructure, all data is included in a full backup.

When an incremental backup is scheduled, the system checks the protected client in specified intervals of time and captures changes in the protected data since the last successful backup (of any type). The diagram below illustrates incremental backups for a client. In this example, the incremental runs once a day, but you can schedule incrementals more frequently if desired.

A differential backup captures changes in the protected data since the last successful full backup. The diagram below illustrates differential backups for a client. Each differential captures all changes in the protected data since the full backup on Day 1. For example, the differential on Day 4 captures all changes since the full backup on Day 1, including the changes that were already captured by the differentials on Day 2 and Day 3.

A synthetic backup is a full or differential backup that the Unitrends system synthesizes by superimposing the incremental backups on the last successful full backup. It then uses the synthesized backups to create recovery points. After the system creates a synthesized full backup, it uses this backup as a reference point when determining whether the client’s protected data has changed and a differential or incremental backup needs to be run.

The Unitrends system uses the following factors to determine when to create a synthetic backup:

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Amount of data being protected on the backup system

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Number of days from the last full backup

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Number of incremental backups since the last full backup

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Load on the system

Synthetic backups are created only for file-level backups and backups of VMware and Hyper-V clients. Synthetic backups are system-side only and do not impact the clients or networks. The diagram below illustrates a synthetic backup. For additional information about synthetic backups, see KB 3560.

A selective backup is run independently of any full, differential, or incremental backup and captures only the client data that you have selected. Selective backups can be used only for file-level backups. For details, see File-level Backups.

For Windows clients, a bare metal backup may be used to capture the boot volume (usually the C: drive) allowing for rapid recovery in the event of a system or drive failure. Note that in Unitrends release 7.4 and higher, regular file-level backups contain this system information, eliminating the need for bare metal backups for many clients. For requirements and details, see Windows Bare Metal Protection. To protect the operating system for non-Windows clients, see Bare metal procedures by client operating system.