Hardware Reference
In-Depth Information
6.1 Introduction
Anyone can build a fast CPU. The trick is to build a fast system.
Seymour Cray
Considered the father of the supercomputer
use every day: search, social networking, online maps, video sharing, online shopping, email
services, and so on. The tremendous popularity of such Internet services necessitated the cre-
ation of WSCs that could keep up with the rapid demands of the public. Although WSCs may
appear to be just large datacenters, their architecture and operation are quite different, as few
shall see. Today's WSCs act as one giant machine and cost on the order of $150M for the build-
ing, the electrical and cooling infrastructure, the servers, and the networking equipment that
connects and houses 50,000 to 100,000 servers. Moreover, the rapid growth of cloud comput-
ing (see
Section 6.5
)
makes WSCs available to anyone with a credit card.
Computer architecture extends naturally to designing WSCs. For example, Luiz Barroso of
Google (quoted earlier) did his dissertation research in computer architecture. He believes an
architect's skills of designing for scale, designing for dependability, and a knack for debug-
ging hardware are very helpful in the creation and operation of WSCs.
At this extreme scale, which requires innovation in power distribution, cooling, monitoring,
and operations, the WSC is the modern descendant of the supercomputer—making Seymour
Cray the godfather of today's WSC architects. His extreme computers handled computations
that could be done nowhere else, but were so expensive that only a few companies could af-
ford them. This time the target is providing information technology for the world instead of
high-performance computing (HPC) for scientists and engineers; hence, WSCs arguably play
a more important role for society today than Cray's supercomputers did in the past.
Unquestionably, WSCs have many orders of magnitude more users than high-performance
computing, and they represent a much larger share of the IT market. Whether measured by
number of users or revenue, Google is at least 250 times larger than Cray Research ever was.
WSC architects share many goals and requirements with server architects:
■
Cost-performance
—Work done per dollar is critical in part because of the scale. Reducing the
capital cost of a WSC by 10% could save $15M.
■
Energy efficiency
—Power distribution costs are functionally related to power consumption;
you need sufficient power distribution before you can consume power. Mechanical system
costs are functionally related to power: You need to get out the heat that you put in. Hence,
peak power and consumed power drive both the cost of power distribution and the cost of
cooling systems. Moreover, energy efficiency is an important part of environmental stew-
ardship. Hence, work done per joule is critical for both WSCs and servers because of the
high cost of building the power and mechanical infrastructure for a warehouse of com-
puters and for the monthly utility bills to power servers.
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