Brazos: A Third Generation DSM System

Brazos is a third generation distributed shared memory (DSM) system designed for x86 machines running Microsoft Windows NT 4.0. Brazos is unique among existing systems in its use of selective multicast, a software-only implementation of scope consistency, and several adaptive runtime performance tuning mechanisms. The Brazos runtime system is multithreaded, allowing the overlap of computation with the long communication latencies typically associated with software DSM systems. Brazos also supports multithreaded user-code execution, allowing programs to take advantage of the local tightly-coupled shared memory available on multiprocessor PC servers, while transparently interacting with remote “virtual” shared memory. Brazos currently runs on a cluster of Compaq Proliant 1500 multiprocessor servers connected by a 100 Mbps FastEthernet. This paper describes the Brazos design and implementation, and compares its performance running five scientific applications to the performance of Solaris and Windows NT implementations of the TreadMarks DSM system running on the same hardware.