Compaq 124708-001 - ProLiant Cluster - 1850 White Paper page 3

TC000602WP
Doc Number
W P
HITE APER
(cont.)
. .
I
. . N T R O D U C T I O N
. .
. .
The enterprise computing systems of many businesses were built around centralized, proprietary
. .
computers, which are expensive to manage and upgrade. The networks that evolved around these
. .
. .
centralized systems use traditional network technologies such as Ethernet and TCP/IP, which are
. .
designed for heterogeneous computing environments. Today, businesses can satisfy their
. .
. .
computing goals with a collection of low-cost, industry-standard servers distributed within a
. .
cluster. A cluster is a group of two or more interconnected servers that act as a single computing
. .
. .
unit. Servers in a cluster can be physically distributed across various locations, yet to a user, the
. .
cluster appears as a single, unified computing resource. In a parallel application cluster, for
. .
. .
example, each server simultaneously runs a copy of an application and the operating system. Client
. .
requests are divided among the servers' CPUs (central processing units), and the servers exchange
. .
. .
information about the portion of the client's request they are processing. If one server fails, the
. .
jobs it was processing are distributed across the remaining servers. Consequently, clustered servers
. .
. .
collectively generate tens of thousands of messages per second to keep track of the jobs they are
. .
. . executing.
. .
. .
The high volume of server-to-server messaging in a cluster requires a very efficient software
. .
communication interface and a highly reliable, high-speed, low-latency hardware interconnect.
. .
. .
Without an efficient server-to-server interconnect, the performance and scalability of a cluster is
. .
severely limited. Traditional network technologies produce excessive software overhead, due to
. .
. .
their heterogeneous environments, and are too inefficient for intense server-to-server
. .
communication. Therefore, in December 1997 Compaq and other industry leaders developed the
. .
. .
Virtual Interface (VI) Architecture specification for a distributed messaging interface that allows
. .
more efficient server-to-server communication through a system area network (SAN). The VI
. .
. .
Architecture provides a common software and hardware interface standard so that customers can
. .
choose the optimum SAN interconnect (Compaq ServerNet II, gigabit Ethernet, cLAN, ATM, or
. .
. .
others).
. .
. .
The Compaq ServerNet II SAN interconnect is the most complete industry-standard
. .
. .
implementation of the VI Architecture specification. Measurement of CPU utilization under
. .
certain conditions shows that ServerNet II provides three times the performance of gigabit Ethernet
. .
. .
and TCP/IP. As a result, ServerNet II is quickly emerging as the interconnect of choice for
. .
implementing clusters of industry-standard servers. Operating system vendor and independent
. .
. .
software vendor support for ServerNet II includes Windows 2000 Data Center, Windows 2000
. .
Advanced Data Server, Linux, and SCO UnixWare 7.1.
. .
. .
. .
. .
T
R A D I T I O N A L
. .
N
E T W O R K S
. .
. .
. .
Clustered servers can communicate with each other by using a traditional network or a SAN.
. .
Traditional network technologies allow several different types of devices to communicate with each
. .
. .
other in complex, heterogeneous networks. Network applications manage communications
. .
between the devices using multipoint protocols like TCP/IP and network interface controllers.
. .
. .
These protocols generate a large amount of software overhead (error checking and control
. .
information) to ensure that messages are sent and received reliably. This software overhead
. .
. .
continually interrupts the servers' CPUs. Consequently, the high volume of server-to-server
. .
messaging in a cluster can overwhelm traditional network protocols like TCP/IP. In fact, clusters
. .
. .
that use traditional networks for messaging can lose as much as 20 to 30 percent of their capability
. .
during intense messaging. This loss of system capability results in slower response times for users
. .
. .
and reduces the scalability, availability, and flexibility of clusters. When you consider the
. .
unpredictable nature of Internet traffic, it becomes apparent that traditional network technologies
. .
. .
cannot handle server-to-server messaging in e-commerce environments.
. .
. .
.
3
N
E T W O R K S V E R S U S
S A
Y S T E M R E A