Front − End Nodes Back − End Nodes SWITCH

Daniel M. Dias William Kish Rajat Mukherjee and Renu Tewari IBM Research Division T. J. Watson Research Center P.O. Box 704, Yorktown Heights, NY 10598 fdias, c1kish, rajatm, c1renu [email protected] Abstract We describe a prototype scalable and highly available web server, built on an IBM SP-2 system, and analyze its scalability. The system architecture consists of a set of logical front-end or network nodes and a set of back-end or data nodes connected by a switch, and a load balancing component. A combination of TCP routing and Domain Name Server (DNS) techniques are used to balance the load across the front-end nodes that run the Web (httpd) daemons. The scalability achieved is quanti ed and compared with that of the known DNS technique. The load on the back-end nodes is balanced by striping the data objects across the back-end nodes and disks. High availability is provided by detecting node or daemon failures and reconguring the system appropriately. The scalable and highly available web server is combined with parallel databases, and other back-end servers, to provide integrated scalable and highly available solutions.