A
machine with four processors is typically more expensive and capable of doing more
work than a single-processor machine; new versions of components, such as CPUs,
are typically faster and often less expensive than older versions.
Online transaction processing (OLTP) systems are most often designed for throughput.
In business intelligence or data warehousing systems, it is often assumed that
CPU and memory are the performance-limiting components. However, CPU processing
power and memory capacity constraints have greatly risen in recent years
(especially in the time period since we wrote earlier editions of this book), and providing
adequate I/O now deserves special attention for these systems as well.
Each system component has a time to access and transport data, or a latency cost.
The latency cost of a component is the amount of latency the use of that component
introduces into the system; in other words, how much slower each successive
level of a component is than its previous level (e.g., Level 2 versus Level 1; see
Table 12-1).
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