Digital Technical Journal, Volume 3, Number 3: Availability in Vaxcluster
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• Availability in VAXcluster Systems • Network Performance and Adapters Digital Technical Journal Digital Equipment Corporation Volume 3 Number 3 Summer 1991 Editorial Jane C. Blake, Editor Kathleen M. Stetson, Associate Editor Leon Descoteaux, Associate Editor Circulation Catherine M. Phillips, Administrator Sherry L. Gonzalez Production Mildred R. Rosenzweig, Production Editor Margaret Burdine, Typographer Peter Woodbury, illustrator Advisory Board Samuel H. Fuller, Chairman Richard W. Beane Robert M. Glorioso Richard]. Hollingsworth John W. McCredie Alan G. Nemeth Mahendra R. Patel E Grant Saviers Victor A. Vyssotsky Gayn B. Winters The Digital Technicaljournal is published quarterly by Digital Equipment Corporation, 146 Main Street ML01-3/B68, Maynard, Massachusetts 01754-2571. Subscriptions to the journal are $40.00 for four issues and must be prepaid in U.S. funds. University and college professors and Ph.D. students in the electri cal engineering and computer science fields receive complimen tary subscriptions upon request. Orders, inquiries, and address changes should be sent to the Digital Technical journal at the published-by address. Inquiries can also be sent electronically to DTJ®CRL.DEC.COM. Single copies and back issues are available for $16.00 each from Digital Press of Digital Equipment Corporation, 12 Crosby Drive, Bedford, MA 01730-1493. Digital employees may send subscription orders on the ENET to RDVAX::JOURNAL or by interoffice mail to mailstop ML01-3/B68. Orders should include badge number, site location code, and address. Allemployees must advise of changes of address. Comments on the content of any paper are welcomed and may be sent to the editor at the published-by or network address. Copyright© 1991 Digital Equipment Corporation. Copying without fee is permitted provided that such copies are made for use in educational institutions by faculty members and are not dis tributed for commercial advantage. Abstracting with credit of Digital Equipment Corporation's authorship is permitted. All rights reserved. The information in the journal is subject to change without notice and should not be construed as a commitment by Digital Equipment Corporation. Digital Equipment Corporation assumes no responsibility for any errors that may appear in the journal. ISSN 0898-901X Documentation Number EY-H890E-DP The following are tmdemarks of Digital Equipment Corporation: Cover Design Bl, CI, DEC, DECconcentmtor, DECdtm, DEC FDD!controller, Our cover graphic represents the shadowing, or replication, of DECnet, DELNl, DSA, DSSI, Digital, the Digital logo, HSC, LAT, Local Area VAXcluster, MSCI� RA, Rdb(VMS, TA, ULTRlX, UNIBUS, data on multiple physicaldisks in a cluster environment. VAX VAX, VAX DBMS, VAX MACRO, VAX RMS, VAX 6000, VAX 9000, VMS host-based volume shadowing pmvides the high data avail VAXcluster, VMS, VMS Volume Shadowing. ability required for applications such as transaction Motorola and 68000 are registered trademarks of Motorola, Inc. processing and is the subject of one of the papers in this issue. Book production was done by Digital's Database Publishing Group The cover was designed by Sandra Calef of Calef Associates. in Northboro, MA. I Contents 5 Fo reword Howard H. Hayakawa and George S. Hoff Availability in VAXcluster Systems Network Performance and Adapters 7 Design of VMS Volume Shadowing Phase II-Host-based Shadowing Scott H. Davis 16 Application Design in a VAXclusterSystem William E. Snaman, Jr. 27 New Availability Features of Local Area VAXcluster Systems Lee Leahy 36 Design of the DEC LANcontroller 400 Adapter Richard E. Stockdale and Judy B. We iss 48 The Architecture and Implementation of a High-performance FDDI Adapter Sat ish L. Rege 64 Performance Analysis of a High-speed FDDI Adapter Ramsesh S. Kalkunte 78 Performance Analysis of FDDI Raj Jain I Editor's Introduction fo r network delay detection and reduction, and fa il ure analysis in local area VA Xcluster systems. The fo cus then moves from VMS-Ievel concerns to the design of network adapters and performance measurement. The adapter described by Dick Stockdale and Judy We iss is the DEC LANcontroller 400, which connects systems based on Digital's XMI bus to an Ethernet LAN. This particular design improves on previous designs by transforming the adapter from a dumb to an intelligent adapter which can off- load the host. Consequently, the adapter supports systems that utilize the fu ll band Jane C. Blake width of Ethernet. The authors provide a system Editor overview, performance metrics, and a critical exam This issue of the Digital Te chnical jo urnalcontains ination of firmware-based design. a collection of papers on two general topics Like the LANcontroller400, the FDDicontroller400 VA Xcluster systems, and network adapters and per is an adapter that interfaces XMI-based systems to a formance. The first set of three papers describes LAN. However, as Satish Rege relates, this adapter new VMS VAX cluster developments and features; was required to transmit data 30 times faster than the second set addresses the topics of LAN adapter Ethernet adapters. Satish discusses the architec design and performance measurement techniques. ture and the choices designers made to address the A common theme across these papers is the devel problem of interfacing a parallel high-bandwidth opment of technologies fo r interconnecting sys CPU bus (XMI) to a serial fi ber-optic network bus tems that offer high data availability without (FDDJ). Their design choices included a three-stage sacrificing performance. pipeline approach to buffe ring that enables these VMS Vo lume Shadowing, described by Scott Davis, stages to proceed in an asynchronous fashion. is a means of ensuring dataavaila bility and integrity To ensure that the perfo rmance goals fo r the in VMS VA Xcluster systems. By maintaining multiple FDDicontroller would be met, a simulation model copies of data on separate devices, the volume was created. In his paper, Ram Kalkunte details the shadowing technique protects data from being modeling methodology, reviews components, and lost as the result of media deterioration or device presents simulation results. Ram describes how in failures. Scott discusses the advantages of the addition to perfo rmance projections, the model new design over controller-based shadowing and provided designers with buffe r sufficiency analysis explains how this fu lly distributed software makes and helped engineers analyze the functional cor a broad range of topologies suitable fo r shadowing. rectness of the adapter design. The growth capabilities and availability of VMS The high level of performance achieved by the VAXcluster systems are characteristics well suited FDDicontroller was driven by the high performance to applications with high-availability requirements. of the FDDI LA N itself- 100 megabits per second. Sanely Snaman first presents an overview of the Raj Jain's subject is performance measurement at VA Xcluster system architecture, including explana the level of the FDDI LAN. Raj describes the perfor tions of the layers, their purpose and function. He mance analysis of Digital's implementation of FDDI then gives practical insights into how the system and how various parameters affect system perfor implementation affects application design and mance. As part of his presentation of the modeling reviews the choices available to application design and simulation methods used, he shares guidelines ers in the areas of client-server computing and data fo r setting the value of one of the key parameters, sharing. target token rotation time, to optimize performance. The availability of applications and cluster con Raj has recently published a book on computer sys figurations is also enhanced by developments in a tems performance analysis, which is reviewed in new release of the VMS operating system. Lee Leahy the Further Readings section of this issue. describes a VMS feature that enables fail-over between multiple LA N adapters and compares this approach to a single-adapter implementation. He then discusses and gives examples of VMS features 2 Biographies I Scott H. Davis Consultant software engineer Scott Davis is the VMS Cluster Technical Director. He is involved in future VMS 1/0 subsystem, VAX cluster, and storage strategies and led the VMS Volume Shadowing Phase II and VMS mixed-interconnect VAX cluster 1/0 projects. Since joining Digital in 1979, Scott worked on RT-11 development and led various real-time operating systems pro jects. He holds a B.S. (1978, cum laude) in computer science and applied mathe matics from the State University of New Yo rk at Albany. Scott is a coinventor for four patents on the shadowing design. Raj Jain Raj Jain is a senior consulting engineer involved in the performance modeling and analysis of computer systems and networks, including VAX cluster, DECnet, Ethernet, and FDDI products. He holds a Ph.D. (1978) from Harvard University and has taught courses in performance analysis at M.l.T. A member of the Authors' Guild and senior member of IEEE, Raj has written over 25 papers and is listed in Who's Who in the Computer Industry, 1989. He is the author of The Art of Computer Sy stems Performance Analysis published recently by Wiley. Ram Kalkunte As a member of the VAX VMS Systems and Servers Group, senior engineer Ram Kalkunte worked on the development of the high performance XMI-to-FDDI adapter. Since joining Digital in 1987, he has also worked on various performance analysis and modeling projects. Ram received a B.E. (1984) in instrumentation engineering from Mysore University in India and an M.S. (1987) in electrical engineering from Worcester Polytechnic Institute. He has a pending patent related to dynamically arbitrating conflicts in a multipart memory controller. Lee Leahy Lee Leahy is a principal software engineer in the VAX cluster group in ALPHA/EVMS Development. He is currently the project leader of the Local Area VAX cluster development effort and was responsible fo r the final design and implementation of the multiple-adapter version of PEDRIVER.