What Causes High Server Load?


Well-Known Member
May 29, 2004
Minneapolis, MN
What is Server Load Average?
The Server Load Average gives the sum of the average number of jobs or active processes in the queue over the last 1, 5, and 15 minutes. It is intended to provide you with a simplistic indication on how much work has been done on your server.

Server Load Average is measured in the x.xx format, with values ranging from 0.00 to potentially unlimited.

Calculated in the UNIX kernel using CALC_LOAD, server load averages are based on exponentially dampened moving averages. New server load average values are in part based on the last server load recordings.

What is an acceptable Server Load Average?
There are a few factors invloved to determine the server average load. If your server(s) use dual processors, the acceptable Server Load Average is 2.00. This load is considered "optimal".

There is no clear-cut Server Load Average number considered to be a 'warning' level for performance degradation. However if the server load gets up to 5.00 or greater for a consistent period of time, then it's worth finding out the exact cause of the higher server load.

Server Load Spikes
It's perfectly normal to have 'spikes' in your Server Load. Peak visitor times, log processing, database backup scripts, automated cron jobs - all can cause 'spikes' in your server load. It's when the server load is constantly above 5.00 - that's the time to start asking questions.

What Causes High Server Load?
There are lots of potential causes of high server loads. Server load levels very much depend on what is being run on your server. The following table gives a good overview of some potential areas which could cause your server to be placed under higher loads.

Possible Causes of High Server Loads
  • High server loads could be caused by just one or several resource-intensive application(s).
    Examples include very high-traffic Web sites, database-driven Web sites, forums, gaming sites, file download sites and so on.
  • A high server load can also be caused by a malicious script or a "runaway script" which can continously loop, dragging down the server's resources.
  • Too many websites on the one server - with the cumulative resources resulting in high server load.
  • Running out of memory and swapping to the swap file.
  • Server backups or server updates are taking place.
  • Misconfigured software causing errors.
  • Users sending large mailing lists.
  • Users trying to bounce spam.
  • Users/spammers sending spam email.
  • Hardware issues including memory leak, bad hard drive, and network card.

This article is a modified version of http://support.newwinnipeg.net/server-load-average.htm
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