178
Networking: A Beginner's Guide
To determine the number of processors you should use for any given task, you
should consult with the maker of both the NOS you plan to use and makers of the
primary applications you plan to run on the server. You might also want to discuss
these issues with other companies that are performing similar work with the proposed
server application. For instance, for a database server for an accounting system that
supports hundreds of users, you should talk to people at other sites that use the same
software and have roughly the same number of users, to learn about their experiences
and suggestions. It's vital to double-check your proposed server configurations in this
way, because different uses of a server might require far more--or far fewer--hardware
resources than you might estimate. If you can find another company doing about the
same thing and with approximately the same load, you can drastically improve your
confidence in a proposed server hardware configuration's ability to meet your needs.
The Intel Pentium Family
Intel's Pentium family has a variety of different processors, ranging from the basic
Pentium all the way up to the Pentium Xeon processor. Current server-class computers
are shipping with Intel Core Duo or Pentium Xeon processors. The Xeon series of
processors are optimized for server-type duties and are more amenable to running in
a multiprocessor system.
Pentium Xeon processors are currently available in speeds ranging up to 2.66 GHz
with up to 6 cores on a single chip. The design of the Xeon processor allows for 8 to
32 processors in a Pentium Xeon system. For certain applications, having such a large
number of processors can be an advantage. The Xeon processor family is packaged in
a Single Edge Contact Cartridge, which is much larger than the packaging used for the
Pentium non-Xeon processors. The Xeon processors also generate quite a bit more heat
than their non-Xeon brethren, mostly due to the much larger cache memory and other
features that boost Xeon processor performance in a server. (It's a good thing that most
servers can monitor their in-case heat levels; sometimes these chips can heat up to more
than 170° Fahrenheit.)
The next big jump in server processors from Intel is coming from its new Itanium
processor family, previously known as the IA-64 architecture. The Itanium family
is based on a 64-bit architecture that uses something Intel calls Explicitly Parallel
Instruction Computing (EPIC). Itanium 2 processors are currently available in speeds
ranging from 1.0 to 1.66 GHz. This architecture relies heavily on compiler techniques
to arrange the byte-level code so that it can execute as efficiently as possible in parallel
(meaning multiple processor instructions execute at the same time).
NOTE
You cannot generally compare the clock speed of processors from one processor family
with the clock speeds of processors from another family to get an idea of their relative performance.
Processors in different families and from different manufacturers work in very different ways from
one another. What takes one processor family four to six instruction cycles to perform might take
another processor family only one instruction cycle. Instead, use clock speeds to get an idea of the
relative speed difference only among processors within a single processor family.