Much Ado About Shared-Nothing

Authors:	M.G. Norman, Th. Zurek, P. Thanisch
Date:	October 1995

Abstract

A parallel computer has a `shared-nothing' architecture if each processor has its own memory and its own disk sub-system; processors communicate by passing messages through an interconnect. It is commonly asserted, by both academic researchers and some of the vendors, that shared-nothingness is the `consensus' architecture for parallel database systems.

We argue that shared-nothingness is no longer the consensus hardware architecture. Furthermore, we question the usefulness of hardware resource sharing as a basis for categorising parallel DBMS software architectures if one wishes to gain some insight into the database's performance characteristics.

We have developed an alternative approach to categorising DBMS software architectures, based on the way that processes and threads are organised to cooperate in transaction and complex query processing. Having developed this model, we then approached ten leading vendors of parallel DBMS products and, for each of the ten, we got the vendor to endorse our description of their architecture in terms of our own processes-and-threads model. Using specific examples, we show that there are major differences between some commercial shared-nothing parallel DBMSs, yet there are important similarities between shared-nothing and shared-disk parallel DBMS products.

Thomas Zurek, <tz@dcs.ed.ac.uk>