User Guide

36 Server Operating System Administration Guide
Server Operating System Administration Guide
103-000148-001
August 30, 2001
Novell Confidential
Manual 99a38 July 17, 2001
The unbalanced system in Figure 4 would benefit noticeably if you were to
upgrade component f to the performance level of g. But if you were to upgrade
f to a performance level beyond g—as shown in the following figure—all
additional performance characteristics in f would be lost because the
bottleneck would move to component g.
Figure 4 Moving the Bottleneck
Thus you derive only a partial return on your investment in the upgrade. To
accomplish more than moving the bottleneck, both components must be
upgraded to the level of h before a full return on investment in h, i, and j can
be reached.
It is useless to test any single component of a system to its fullest capacity
without allowing for the possibility that another component is actually
bottlenecking system performance. You can upgrade system components, but
you won’t see any significant improvement until you isolate the system
bottleneck, assess its relationship to the performance characteristics of the
entire system, and take appropriate action.
Bottleneck isolation is critical if you’re building high-performance systems.
You need to know how and where your system is bottlenecking. Moreover,
you need to know how tightly that bottleneck is coupled with the performance
characteristics of the rest of the system. If the poorly performing component
is in a different performance category than the other components, you might
obtain a greater return on investment by making the necessary upgrades to
move the bottleneck to the highest possible performance level.
This discussion is taken from "Performance Analysis: Isolating the Real
Bottleneck in a System," in the January 1996 AppNotes
TM
(http://
developer.novell.com/research/appnotes/1996/january/04/index.htm).
Upgrade f (partial return on investment)
f ghij
Lower
Performance
Higher
Performance