Implementation of a Parallel Ynet Architecture

A simulation of an alternate implementation of a redundant busing network based on the Teradata Ynet architecture is presented. An overview of the Teradata DBC/1012 data base parallel processing computer including the Ynet, an active logic busing network, is given. Other multiprocessor busing networks are examined and compared to the standard Ynet and the alternate Ynet. In the standard Ynet system, two networks, called Ynets, process message packets concurrently. When one of the Ynet paths fails, the system is reset. The remaining Ynet path restarts using the previously interrupted packets and processing continues without the aid of the failed Ynet. In the implementation presented here, the two busing networks process the message packets in parallel. Now, when one of the Ynet paths fails, the other continues processing the packets without interruption. This implementation can be referred to as a parallel Ynet. The advantages and disadvantages of the parallel Ynet are discussed and suggestions for further research are given. Listings and sample outputs are included in the appendices

Fault diagnosis of distributed systems : analysis, simulation and performance measurement.

Fault diagnosis forms an essential component in the design of highly reliable distributed computing systems. Early models for diagnosis require a global observer, whereas the diagnosis is shared between the systems nodes in later models. These models are reviewed and their different diagnosability properties reconciled. The design of improved fault diagnosis algorithms for systems without a global observer provides the main motivation for the thesis. The modified algorithm SELF3 [Hoss88] is taken as a starting point. A number of communication architectures used in distributed systems are reviewed. The properties of diagnosis algorithms depend strongly on the testing graph. A general class of testing graphs, designated as H-graphs, (which are a generalization of Dꞩṭ graphs introduced in [Prep67]), are investigated and their diagnostic properties determined. A software simulator for distributed systems has been written as the main investigative tool for diagnosis algorithms. The design and structure of the simulator are described. The diagnosis process is measured in terms of diagnostic time and number of messages produced, and the factors upon which these quantities depend are identified. The results of simulation of a number of systems are given under various fault conditions. A modified way of routing diagnosis messages, which, especially in large system s, results in a reduction in both the number of diagnosis messages and the time required to perform diagnosis, is presented. The thesis also contains a number of specific recommendations for improving existing self-diagnosis algorithms