The Pegasus project reflects our belief that if distributed multimedia is to be supported effectively, a holistic approach to system design is required. Multimedia is not just a bolt on; it requires a fundamental reexamination of most aspects of the infrastructure. We have thought carefully about integrating multimedia devices into the network architecture of the system, we have looked at the data paths from camera lens to display screens, and we have analysed storage infrastructures from a performance, reliability and consistency perspective.
Thus far we have found that this approach gives a clean system design and makes our implementations efficient and simple. The desk-area network as the connecting infrastructure for machines and devices has greatly simplified the architecture of the rest of the system.
In the storage service, we have discovered that techniques for consistent caching, data buffering, log structure and RAID, each of which, by itself, is difficult to integrate in an existing environment, can be combined in a new storage system architecture. Consistent caching, buffering and RAID gave us reliability (no data loss in a single crash); log structure and RAID give us good write performance.
Pegasus is only half-way through its funding period now and a lot of work still needs to be done. We hope we can demonstrate a complete system in two years' time. The results of our project are naturally public and we intend to make all code available where it is not restricted by licences from others.