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WHITE PAPER (cont.)
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. I N T R O D U C T I O N
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. The enterprise computing systems of many businesses were built around centralized, proprietary
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. computers, which are expensive to manage and upgrade. The networks that evolved around these
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. centralized systems use traditional network technologies such as Ethernet and TCP/IP, which are
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. designed for heterogeneous computing environments. Today, businesses can satisfy their
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. computing goals with a collection of low-cost, industry-standard servers distributed within a
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. cluster. A cluster is a group of two or more interconnected servers that act as a single computing
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. unit. Servers in a cluster can be physically distributed across various locations, yet to a user, the
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. cluster appears as a single, unified computing resource. In a parallel application cluster, for
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. example, each server simultaneously runs a copy of an application and the operating system. Client
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. requests are divided among the servers’ CPUs (central processing units), and the servers exchange
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. information about the portion of the client’s request they are processing. If one server fails, the
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. jobs it was processing are distributed across the remaining servers. Consequently, clustered servers
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. collectively generate tens of thousands of messages per second to keep track of the jobs they are
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. executing.
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. The high volume of server-to-server messaging in a cluster requires a very efficient software
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. communication interface and a highly reliable, high-speed, low-latency hardware interconnect.
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. Without an efficient server-to-server interconnect, the performance and scalability of a cluster is
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. severely limited. Traditional network technologies produce excessive software overhead, due to
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. their heterogeneous environments, and are too inefficient for intense server-to-server
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. communication. Therefore, in December 1997 Compaq and other industry leaders developed the
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. Virtual Interface (VI) Architecture specification for a distributed messaging interface that allows
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. more efficient server-to-server communication through a system area network (SAN). The VI
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. Architecture provides a common software and hardware interface standard so that customers can
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. choose the optimum SAN interconnect (Compaq ServerNet II, gigabit Ethernet, cLAN, ATM, or
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. others).
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. The Compaq ServerNet II SAN interconnect is the most complete industry-standard
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. implementation of the VI Architecture specification. Measurement of CPU utilization under
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. certain conditions shows that ServerNet II provides three times the performance of gigabit Ethernet
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. and TCP/IP. As a result, ServerNet II is quickly emerging as the interconnect of choice for
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. implementing clusters of industry-standard servers. Operating system vendor and independent
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. software vendor support for ServerNet II includes Windows 2000 Data Center, Windows 2000
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. Advanced Data Server, Linux, and SCO UnixWare 7.1.
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R A D I T I O N A L N E T W O R K S V E R S U S S Y S T E M A R E A
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. N E T W O R K S
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. Clustered servers can communicate with each other by using a traditional network or a SAN.
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. Traditional network technologies allow several different types of devices to communicate with each
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. other in complex, heterogeneous networks. Network applications manage communications
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. between the devices using multipoint protocols like TCP/IP and network interface controllers.
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. These protocols generate a large amount of software overhead (error checking and control
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. information) to ensure that messages are sent and received reliably. This software overhead
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. continually interrupts the servers’ CPUs. Consequently, the high volume of server-to-server
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. messaging in a cluster can overwhelm traditional network protocols like TCP/IP. In fact, clusters
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. that use traditional networks for messaging can lose as much as 20 to 30 percent of their capability
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. during intense messaging. This loss of system capability results in slower response times for users
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. and reduces the scalability, availability, and flexibility of clusters. When you consider the
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. unpredictable nature of Internet traffic, it becomes apparent that traditional network technologies
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. cannot handle server-to-server messaging in e-commerce environments.
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Doc Number TC000602WP
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