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Chapter 2. Resource Monitoring

2.5.4. The Sysstat Suite of Resource Monitoring Tools

While the previous tools may be helpful for gaining more insight into system performance over very

short time frames, they are of little use beyond providing a snapshot of system resource utilization. In

addition, there are aspects of system performance that cannot be easily monitored using such simplistic

tools.

Therefore, a more sophisticated tool is necessary. Sysstat is such a tool.

Sysstat contains the following tools related to collecting I/O and CPU statistics:

iostat

Displays an overview of CPU utilization, along with I/O statistics for one or more disk drives.

mpstat

Displays more in depth CPU statistics.

Sysstat also contains tools that collect system resource utilization data and create daily reports based

on that data. These tools are:

sadc

Known as the system activity data collector,

sadc

collects system resource utilization informa 

tion and writes it to a file.

sar

Producing reports from the files created by

sadc

,

sar

reports can be generated interactively or

written to a file for more intensive analysis.

The following sections explore each of these tools in more detail.

2.5.4.1. The

iostat

command

The

iostat

command at its most basic provides an overview of CPU and disk I/O statistics:

Linux 2.4.18 18.8.0 (pigdog.example.com)

12/11/2002

avg cpu:

%user

%nice

%sys

%idle

6.11

2.56

2.15

89.18

Device:

tps

Blk_read/s

Blk_wrtn/s

Blk_read

Blk_wrtn

dev3 0

1.68

15.69

22.42

31175836

44543290

Below the first line (which displays the system's kernel version and hostname, along with the current

date),

iostat

displays an overview of the system's average CPU utilization since the last reboot. The

CPU utilization report includes the following percentages:

Percentage of time spent in user mode (running applications, etc.)

Percentage of time spent in user mode (for processes that have altered their scheduling priority

using

nice(2)

)

Percentage of time spent in kernel mode

Percentage of time spent idle

Below the CPU utilization report is the device utilization report. This report contains one line for each

active disk device on the system and includes the following information: