The operation principles and general structure of the FastBack repository pool

The FastBack repository is presented as a repository pool. Repository pool is a term for a virtual storage, which consists of physical repository units such as disks, volumes, folders or network shares.

The FastBack repository may consist of one or more similar or different repository units.

Figure 1: An example of the structure of a repository pool

The repository pool structure is similar to the RAID 0 principle of data storage with 1 x repository unit being a vital part of the global pool. Once a disk, volume, folder or network share is added as a part of the repository pool, it can only be removed by using the FastBack Manager official procedure, as described in the FastBack user guide.

Once a new unit is added to the repository pool, the FastBack server creates the required configuration and index file in the repository pool. If a disk is added to the repository pool, special information is written to its NTFS sector 0.

The FastBack snapshot (JOB) data is stored in the repository pool in "JOB<number>" folders. The same JOB data may be located on one repository unit, or maybe separated between different repository units' folders.


Figure 2: A general example of repository pool content storage

When a repository unit (disk, folder, volume or network share) becomes unavailable (disconnected unexpectedly, or not removed according to the FastBack repository unit removal procedure, etc.), the whole FastBack application operation might be stopped. The FastBack server enters the "Limited mode", the snapshots don't run, configuration changes and updates are unavailable etc. Previously backed up data can be corrupted or lost.


Figure 3: An example of faulty repository pool with a removed repository unit

As seen on the example (Figure 3) a repository unit (folder) was improperly removed from the repository pool. This makes the whole repository pool operate incorrectly and causes the FastBack server to enter the "Limited mode".

Possible solutions:

1) When a repository unit was removed unexpectedly (for example, when a network share or disk storage used as repository units were disconnected) and the repository unit still contains the unchanged repository data (FastBack configuration files, JOB folders etc.) the problem can be solved by stopping the FastBack Server service. Then you reconnect the problematic repository unit and make it available and visible inside of Windows. You then restart the FastBack server service.

2) When a repository unit becomes unavailable unexpectedly and, as the result, the repository unit content is damaged, missing or corrupted, the problem can be solved only by re-installing the FastBack Server, by cleaning (or re-formatting) the whole repository pool and by re-defining it as new and clean repository pool in the FastBack Server.