On Fri, Feb 16, 2007 at 12:31:16PM -0600, James Wade wrote:
Can I set the vmstat collection to average less and collect more data points?
You can change the collection to run every 15 seconds, but you will have to change the RRD file definition also so it knows that you intend to feed it data that often. Otherwise it will just discard your extra datapoints.
The users here don't agree with the CPU Utilization Graph, they don't like the way the Average doesn't fluctuate much.
Basically, they are comparing the Load graph with the Utilization Graph and want to see the graph correlate more with the Load Graph.
Your users are comparing apples and oranges - those two numbers have very little to do with each other.
Here's the explanation of the "load average" that you see in the "Load" graph:
System load averages is the average number of processes that are
either in a runnable or uninterruptable state. A process in a
runnable state is either using the CPU or waiting to use the CPU.
A process in uninterruptable state is waiting for some I/O access,
eg waiting for disk. The averages are taken over the three time
intervals. Load averages are not normalized for the number of
CPUs in a system, so a load average of 1 means a single CPU system
is loaded all the time while on a 4 CPU system it means it was idle
75% of the time.The CPU utilisation graph IS normalized over the number of CPUs - that in itself makes a difference (unless you have single CPU systems). But more importantly, a process will show up on the "CPU utilisation" graph ONLY when it is using CPU time; and it will show up on the "load average" graph when it is using CPU time, AND when it is waiting to be scheduled for some CPU time, AND while it is waiting for I/O to complete.
Since most server tasks are very I/O bound you will often see little correlation between the two graphs. In fact, if the correlation becomes too close it is usually a sign that your system needs more CPU power.
Regards, Henrik