Long-Term Persistence

In general we differentiate between the capability to access the bit information (bit stream) on a storage medium, and its interpretability (the stream of bits a video or a text etc). Here we will limit ourselves on discussing methods of bit-stream preservation, since guaranteeing interpretability is a huge and unsolved problem influenced by many factors.

Our current opto-magnetic storage media has a very limited life-time. Due to the high technological innovation rate, we have to speak about effective life-times of no longer than 5 to 10 years, dependent on the type of media. After this period, either the storage media (the disks and tapes) have deteriorated, or the access technology is no longer available, except in highly specialized institutions. In addition, our storage media is very unreliable in so far that disks can crash, magnetic tapes could break, etc. To compensate for these two phenomena that endanger the persistence of the stored material, the DOBES archive, as well as other archives, applies two strategies:

• at regular intervals the storage technology has to be updated to more modern equipment
• the data has to be distributed to many places.

Equipment Migration

The MPI team has just updated its whole storage, server and network architecture to new technology. The major components will be replaced within a timeframe of 5 years, except the tape library, for which we assume a life-time of about 8 to 10 years. A description of the setup can be found here.

Resource Distribution

As indicated, it is important to create as many copies as possible and distribute them around the world. Currently, all DOBES resources are available in seven copies:

• at the MPI, two copies are created dynamically at different storage media and different locations in the building
• a copy is distributed dynamically to the GWDG in Göttingen (Germany), which is one of the big computer centers of the Max-Planck-Society and which itself has a double storage strategy
• another copy is distributed dynamically to the RZG in Garching-Munich, which is the other big computer center of the Max-Planck-Society and which also has a double storage strategy (exchange of all data with the Leibniz Computer Center)
• another copy is distributed dynamically to the MPI for evolutionary Anthropology in Leipzig.

For the archived data in the two computer centers of the MPS the president has given a 50 year institutional guarantee.

The DOBES archive is member of the DELAMAN network, which is working on methods that allow the exchange of data at a world wide level. It participates in the European DAM-LR project that is working on Grid technology allowing an easy exchange and a distributed access.