Raheel Syed:

Interesting series Part 2: Understanding Linux Load Average

Originally posted on The Dutch Prutser's Blog:

In part 1 we performed a series of experiments to explore the relation between CPU utilization and Linux load average. We came to the conclusion that CPU utilization clearly influences the load average. In part 2 we will continue our experiments and take a look if disk I/O also influences the Linux load average.

Disk I/O and load average

The first experiment is starting 2 processes performing disk I/O on an otherwise idle system to measure the amount I/O issued, the load average and CPU utilization using the sar command. BTW: My load-gen script uses the dd command to generate disk I/O.

$ load-gen disk 2
$ sar –b 30 6
Linux 2.6.32-300.20.1.el5uek (roger.example.com) 04/21/2012

09:26:59 PM tps rtps wtps bread/s bwrtn/s
09:27:29 PM 24881.59 0.00 24881.59 0.00 46776.38
09:27:59 PM 26894.34 0.00 26894.34 0.00 50553.80
09:28:29 PM 26772.19 0.10 26772.09 0.80 50327.21
09:28:59 PM 27366.10 0.00 27366.10 0.00 51438.92

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About Raheel Syed

Oracle DBA
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