Clusters and distributed systems offer fault tolerance and high performance through load sharing, and are thus attractive in real-time applications. When all computers are up and running, we would like the load to be evenly distributed among the computers. When one or more computers fail the must be redistributed. The redistribution is determined by the recovery scheme. The recovery scheme should keep the load as evenly distributed as possible even when the most unfavorable combinations of computers break down, i.e. we want to optimize the worst-case behavior. In this paper we define recovery schemes, which are optimal for a number of important cases. We also show that the problem of finding optimal recovery schemes corresponds to the mathematical problem of finding sequences of integers with minimal sum and for which all sums of subsequences are unique.
Abstract. This chapter presents experiences from five large performancedemanding industrial applications. Performance and maintainability are two prioritized qualities in all of these systems. We have identified a number of conflicts between performance and maintainability. We have also identified three major techniques for handling these conflicts. (1) By defining guidelines for obtaining acceptable performance without seriously degrading maintainability. (2) By developing implementation techniques that guarantee acceptable performance for programs that are designed for maximum maintainability. (3) By using modern execution platforms that guarantee acceptable performance without sacrificing the maintainability aspect. We conclude that the relevant performance question is not only if the system meets its performance requirements using a certain software design on a certain platform. An equally interesting question is if the system can be made more maintainable by changing the software architecture and compensating this with modern hardware and/or optimized resource allocation algorithms and techniques.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.