Don Harbert,
Vice President,
UNIX Business

Digital not only invented clusters but continues to set the standard by which all other cluster systems are measured. The VAXcluster success and that of Digital's latest UNIX cluster systems derive from superb engineering that builds on the system definition put forth in the early 1980s by the VAX engineering team: an available, extensible, high-performance multicomputer system built from standard processors and a general-purpose operating system, with characteristics of both loosely and tightly coupled systems.[*]

We in the UNIX community are proud of our VAXcluster heritage and have engineered our products to provide the same kinds of benefits to customers that VAXcluster systems provide.[+] In the opening paper for this issue of the Journal, members of the Digital UNIX engineering team describe the multicomputer system for the Digital UNIX environment, called TruCluster, which, like the VAXcluster system, is designed for high availability, scalability, and performance.

The technology, of course, is different, and the environment is open. The fundamental concepts are nevertheless the same. The TruCluster system is a loosely coupled, general-purpose system connected by a high-performance interconnect. It maintains a single security domain and is managed as a single system. Cluster services remain available even when other members are unavailable. Like VAXcluster systems, TruCluster systems implement a distributed lock manager, which provides synchronization for a highly parallelized distributed database system. The technology for the lock manager, however, is newly implemented for the UNIX environment. Also completely new is the interconnect technology for TruCluster systems. MEMORY CHANNEL is a reliable, high-speed interconnect based on a design by Digital partner Encore Computer Corporation. MEMORY CHANNEL addresses the unique needs of clusters by implementing clusterwide virtual shared memory; the interconnect reduces overhead and latency by two to three orders of magnitude.[**] Because MEMORY CHANNEL uses the industry-standard PCI, designers can implement the network at very low cost. We believe this interconnect technology puts Digital years ahead of the competition.

The TruCluster system is the latest example of Digital's intent to remain a technology leader in the UNIX market. We began by developing the first high-performance, 64-bit general-purpose operating system, DEC OSF/1, shipping in March 1993. The first Digital UNIX cluster release, DECsafe Available Server Environment, followed soon thereafter in April 1994. The announcement in April 1996 of TruCluster systems with MEMORY CHANNEL again places Digital far ahead of the competition technologically. The performance of these available cluster systems now approaches that of very expensive supercomputers. System performance has been measured at the record-breaking rate of 30,390 tpmC on four AlphaServer 8400 systems running Digital UNIX and the Oracle Universal Server with Oracle Parallel Server. The previous performance record, 20,918 tpmC, was held by the proprietary Tandem Himalaya K10000-112; Digital's open system cluster performance record is 1.5 times the Tandem performance record at one-third the system cost.

For Digital, clusters of high-performance 64-bit systems are to a great extent at the heart of its commercial and technical server strategy. Digital UNIX has been defined and engineered for the server business, specifically, for the high-performance commercial and large-problem/scientific environment. To be successful in the open system market, however, a company must reach outside itself to jointly engineer products with leading software suppliers that have the software customers need to be competitive. Therefore, the first TruCluster implementation is designed with Digital's partners -- major software companies -- to meet the requirements for high-performance and functionality in the commercial database server market.

The competitive challenge now is to maintain Digital's significant lead in providing outstanding cluster performance, availability, and affordability. From a technological perspective, the immediate and achievable goal is to increase the number of cluster nodes from 4 to 10 or 20 nodes. Within this range, Digital maintains a simple cluster system model that offers the performance advantages of clustering and avoids the disadvantages, such as the management problems and qualification headaches, of more complex topologies. Further, The Digital UNIX organization will focus on a new cluster file system, configuration flexibility, management tools, and a cluster alias that allows a single-system view for clients and peers. The overall goal of this work is to evolve toward a more general computing environment.

The kinds of tools that both simplify and enhance performance are exemplified by the program analysis and optimization tools presented in this issue. Built on Digital UNIX version 4.0 and announced in April, these tools help software developers extract maximum performance from the system. The story of the tools development is an excellent example of the direct application of research to products. The power of the OM object modification tool and the analysis tool with object modification (Atom) was recognized by developers even as research progressed; in fact, semiconductor designers developed Atom tools to evaluate new Alpha chip implementations. The result of this close cooperation between research and development is advanced programming tools for customers.

These efforts in the UNIX organization are manifestations of Digital's commitment to open systems. Other areas of engineering where this commitment is apparent are also represented in this issue. For example, eXcursion software is key to integration between Microsoft's Windows family of products and Digital's UNIX and OpenVMS products. This wholly revised version both adds new functionality and conserves system resources. Another major area of strength for Digital is its networks products. Networks engineers describe two examples of network services that increase users' choices and extend system functionality, i.e., the Integrated Directory Services (IDS) and the Common Directory Interface.

Digital's strategy is to continue to engineer products that provide outstanding performance and price/performance in open environments. In all areas of engineering -- systems, services, networking -- our goal is to set the standard by which all others are measured.

* Nancy P. Kronenberg, Henry M. Levy, and William D. Strecker, "VAXclusters: A Closely-Coupled Distributed System," ACM Transactions on Computer Systems, vol. 4, no. 2 (May 1986): 130-146.

+ Digital has renamed VAXcluster systems to OpenVMS cluster systems.

** Richard B. Gillett, "Memory Channel Network for PCI," IEEE Micro (February 1996) 12-18.