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I use 'htop' to monitor my web server. It's recently quite loaded and the Load average is showing something like this:

Load average: 3.10 2.56 1.63

I searched the web about these numbers and I found an article about it: http://blog.scoutapp.com/articles/2009/07/31/understanding-load-averages

In the article, it says if I have 2 CPUs, 2.0 means 100% CPU utilization.

And my VPS has two CPUs, so what does 3.1 mean? How could it exceed 100% CPU utilization?

And from these numbers, does it mean I should be wary about the loading now? But the performance seems totally fine, and this is a managed VPS, the hosting company has not notified me any warning about it.

During day time, Load average always show these high numbers... here is another snapshot while writing.

Load average: 3.03 2.77 1.97

Load average: 0.41 1.29 1.60 <---- 5 more minutes later

So I am wondering how much room left for this site to grow in current configurations? What kind of proactive actions I should take in advance?

I don't want to wait until the server bursts.

Thanks.

Community
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Joe Huang
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2 Answers2

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3.1 means that on average there are 3.1 processes either using the CPU, waiting for it, or waiting for I/O to complete. It's not a measure of CPU utilization but of load.

The load average is just one piece of information. It doesn't really tell you much by itself. Have a competent server administrator analyze the server's behavior to assess how well it's handling the load it's being given.

David Schwartz
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4

The best proactive action you can take is to install a monitoring/graphing tool like Cacti, Zabbix, Nagios, Munin or Observium. (There are other choices available.)

Track load average, CPU utilisation, I/O stats, memory usage, HTTP requests per second and anything else you can think of. With the graphs, you will often be able to predict and prevent downtime before it happens.

Most tools also provide alerts on thresholds such as "Less than 5% disk space remaining" which can very quickly let you home in on the source of the downtime.

These tools will be less effective if you only have one box.

Ladadadada
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