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uptime is the easiest way to check the load average. Just run "uptime" at the prompt.
The uptime utility displays the current time, the length of time the system has been up, the number of users, and the load average of the system over the last 1, 5, and 15 minutes.
Short spikes are normal, and a good number is anything under 1 (0.8, etc). If it's a script heavy box or a Mysql heavy box, you may see that number consistently stay a bit higher, but if it constantly stays above 10, you have a problem.
Also, uptime is computed based on a couple of things, but mostly on the number of processes in a "wait" state. In other words, the number of processes that are waiting for their chance to run, so this means that if the load average is too high, you have processes that aren't being handled immediately, which translates into a slower server.
You can watch the server performance by running vmstat. For instance, to see 100 1 second snapshots, run "vmstat -c 100". You'll see something like the following
procs memory page disks faults cpu
r b w avm fre flt re pi po fr sr ad0 md0 in sy cs us sy id
26 1 0 558508 38644 319 0 0 0 17 25 0 0 277 19 317 5 5 90
The third column (w) is the processes in the wait state. Ideally, this number should almost always be 0. Do "man vmstat" to see what the rest of the numbers mean. vmstat is a good diagnostics tool to see if your swapping, if your disks are keeping up, etc.
Hope this helps...
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