Typical Unix System Parameters

Typical Unix System Parameters

Copyright(c) Management Analytics, 1995 - All Rights Reserved

Copyright(c), 1990, 1995 Dr. Frederick B. Cohen - All Rights Reserved

Most UNIX systems have modifiable operating system parameters that allow the systems administrator to control performance to meet usage requirements. We will now list some typical parameters (taken from System 5 UNIX), and describe how they might affect performance.

There are usually about 50 tunable parameters on a UNIX system, and we have only touched on a few of them here. We are not trying to be comprehensive, and parameters differ from system to system so these won't necessarily apply to your system, but the concepts are the same. Each parameter impacts performance in a way that depends on the available physical resources and the system usage patterns. When combined, these parameters form a complex tradeoff space, but there are some guiding principles that will help you along the way.

Most UNIX systems provide performance analysis tools to help understand what is dictating system performance. For example, performance tools will tell you what percentage of the system time is spent in paging or swapping, how many file open failures occur as a result of inode limits, and other information that will help you find bottlenecks. Once a bottleneck has been identified, it should be pretty straight forward to find parameters related to the bottleneck and do simple experiments to find techniques for improvement.

Ultimately, the physical time and space available may simply be inadequate for your needs. In this case, you may have to add physical resources to improve performance. For example, if the number of paging faults is enormous and all related parameters have been adjusted, and the software is at its best configuration to minimize paging, you may need to add memory. If this is not possible, you may have to purchase another computer or change your usage characteristics to get the desired performance.