I am currently
evaluating Servers Alive and trying to duplicate some of the tools that I
currently use.
Presently, I use a Performance Monitor set to an 14 minute
interval to track processor utilization so I can look at 24 hour trends. I set
Servers Alive up to monitor the same WMI counters, but on a two minute interval,
then used RRDTool to log and plot the results. The output graphs are markedly
different between Servers Alive and Perfmon. I have created a quick webpage with examples of the
graphs, note especially the SVR-MAIL lines.
The Servers
Alive/RRDTool output is very erratic in nature, whereas the perfmon output is
smoother with only the occasional spike during expected high usage times like
backups. If I look at the actual results, two of the four
machines often return a value of 0 for Processor Usage for one or
both. Performance Monitor doesn't seem to record zero values, if I look at
the counter, there is always a minimum value greater than
zero.
Roundtrip times are
on the order of 200 ms whether a zero is returned or a value, timeout is left at
default. I've got logging turned on, but don't see any errors. All
counters return non-zero values at times, so it looks like they are
set up at least partially correct. The other counters will occasionally return a
zero and all will occasionally also return very small numbers like 0.00128.
Servers alive is being run as a domain admin, so permissions should be
okay.
From reading the Microsoft
documentation, Processor Usage is calculated over a "sample interval". It is
unclear to me if the interval is preset or part of the WMI query. Perhaps
perfmon is looking at an average over a large number of seconds and Servers
Alive is getting closer to instantanious results.
I can smooth the
data by plotting a trend, but I would like to know why the data is so different.
Are there tweaks or other methods to get more consistent output? Am I
trying to fix something that isn't broken?
Casimir
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