AIX performance monitoring: IO system bottleneck analysis

Input/output (I/O) bottlenecks

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1. Iostat

The Iostat command is used to count CPU usage and the amount of i/0 for TTY devices, hard disks, and CD-ROMs.

To run the command:

Iostat 5 10

10 statistical results are displayed, one of the following data:

Tty:tin tout avg-cpu:% user% SYS% IDLE% iowait

0.0 102.2 0.2 0.7 99.0 0.1

Disks:% tm_act Kbps TPS Kb_read KB_WRTN

Hdisk2 0.0 0.0 0.0 0 0

Hdisk3 0.0 0.0 0.0 0 0

Hdisk0 0.4 33.8 2.6 0 172

Hdisk1 0.0 2.4 0.6 0 12

cd0 0.0 0.0 0.0 0 0

which

%iowait% CPU idle time while waiting for local I/O

%idle% CPU idle time without waiting for local I/O

The CPU time attribute is labeled iowait when there is no process to use the CPU but at least one process is waiting for I/O.

If the percentage of iowait time is high, sample shows that the disk input and output (I/O) is the main cause of the slow running of the system.

%tm_act the percentage of hard disk busy

Note: The Tm_act value is high, indicating that there is an I/O bottleneck on the hard drive.

When%tm_act (hard drive busy time) is high, you may feel that the system is running at a slower rate. System performance is affected by the%tm_act value of a hard disk on some systems that is 60% or higher.