Here is a really nice article on how to think about load average, using a traffic analogy:
http://blog.scoutapp.com/articles/2009/07/31/understanding-load-averages As others have pointed out, if your CPU usage numbers are low and load average is high, you are most likely I/O bound (e.g. disk or network I/O). To determine what is causing your computer to be I/O bound, you can use atop, iotop, iostat, dstat, etc. Another way to tell that a system is I/O bound using regular "top" command is to press "1" while running "top" to split the stats by CPU core. For each CPU core, "top" will show %us (user time) %sy (system time) %id (idle) %wa (I/O wait) etc. Here is a CPU bound example. In the top output below, I'm running the "openssl speed" benchmark, and you can see one of the cores is using 100%us: top - 09:44:26 up 8 days, 17:22, 5 users, load average: 0.95, 0.61, 0.26 Tasks: 227 total, 3 running, 222 sleeping, 0 stopped, 2 zombie Cpu0 : 12.6%us, 0.7%sy, 0.3%ni, 86.4%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu1 :100.0%us, 0.0%sy, 0.0%ni, 0.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st And here is an I/O bound example. I'm running "sudo dd if=/dev/sda of=/dev/null". You can see that the %wa times are relatively high, as is the load average: top - 09:53:17 up 8 days, 17:30, 6 users, load average: 2.61, 1.06, 0.47 Tasks: 229 total, 1 running, 226 sleeping, 0 stopped, 2 zombie Cpu0 : 6.0%us, 11.6%sy, 1.3%ni, 3.0%id, 77.8%wa, 0.0%hi, 0.3%si, 0.0%st Cpu1 : 10.9%us, 5.6%sy, 0.3%ni, 52.3%id, 30.8%wa, 0.0%hi, 0.0%si, 0.0%st On my Ubuntu desktop, I always have the System Monitor panel installed and configured to show I/O wait times as well as network and disk I/O at a glance. I usually set the I/O wait color to purple to let me know at a glance whether my laptop is CPU or disk I/O or network I/O bound. In the attached screenshot taken during the "dd" command above, you can clearly see that the I/O wait time is dominating, as is disk I/O. Cheers Paul
