Completed on 17 October 2007 by Felix Kronlage.

• Prof. Dr.-Ing. Oliver Theel
  
• Dipl.-Inform. Philipp Hahn

• Distributed file systems

Hard disc space is available in abundance on most computers in use today. Although the space requirements of many applications have also increased, the requirements of office software are rather modest. They prefer to be guaranteed that business-critical documents will still be available, at least in an older version, even after a system crash or accidentally overwritten files.

In a distributed system, further problems and possibilities also arise: Changes made on one computer usually have to be updated on one or more other computers, for which the files can be transferred in full or only the interim changes. On the other hand, the storage space that is often available anyway offers the possibility of storing further versions of a file, so that even if one computer fails, the data is still accessible(possibly at least in an older version).

There are already several solutions for synchronising computers, such as rsync and unison under UNIX or Linux. However, both require that the computers involved in a synchronisation process can communicate with each other online. Although high-speed data networks are often used, where the computers can communicate with each other at any time, communication can be considerably slower, more expensive or even undesirable, especially with mobile devices or in the area of high-security systems.

As part of the work, a framework for the efficient synchronisation of several computers that cannot communicate with each other constantly is to be created. In addition to the possibility of online synchronisation in resource-limited situations (short time windows, low bandwidth, long message runtimes), offline synchronisation should also be possible where possible, in which messages are (or can only be) transmitted in one direction. The practicability of the developed solution is to be substantiated by experiments, among other things. The cost/benefit aspect is to be demonstrated and evaluated using suitable comparative measurements with current existing methods.

• BS1
• BS2
• (VBS)

The work contains practical elements.