Hardware Reference
In-Depth Information
Figure 1-10.
A printed circuit board is at the heart of every personal computer.
This one is the Intel DQ67SW board. © 2011 Intel Corporation. Used by permis-
sion.
Clusters
Owing to almost continuous improvements in the price/performance ratio of
servers, in recent years system designers have begun connecting large numbers of
them together to form
clusters
. They consist of standard server-class systems con-
nected by gigabit/sec networks and running special software that allow all the ma-
chines to work together on a single problem, often in business, science or engineer-
ing. Normally, they are what are called
COTS
(
Commodity Off The Shelf
) com-
puters that anyone can buy from a PC vendor. The main addition is high-speed net-
working, but sometimes that is also a standard commercial network card, too.
Large clusters are typically housed in special-purpose rooms or buildings cal-
led
data centers
. Data centers can scale quite large, from a handful of machines to
100,000 or more of them. Usually, the amount of money available is the limiting
factor. Owing to their low component price, individual companies can now own
such machines for internal use. Many people use the terms ''cluster'' and ''data
center'' interchangeably although technically the former is the collection of servers
and the latter is the room or building.
A common use for a cluster is as an Internet Web server. When a Website ex-
pects thousands of requests per second for its pages, the most economical solution
