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From herrold@owlriver.com Thu Nov 28 12:42:01 2002
Date: Wed, 13 Nov 2002 14:08:55 -0500 (EST)
From: R P Herrold <herrold@owlriver.com>
Reply-To: k12osn@redhat.com
To: k12osn@redhat.com
Subject: [K12OSN] Capacity analysis - cron, SNMP, or what?

new subject alert.

On Wed, 13 Nov 2002, Jan Wilson wrote:

> workstation, it MAY be adequate. Best advice: stick as much RAM into
> the server as possible, and use the 256 MB + 50 MB per workstation as
> a very crude minimum.
<snip>
> access or CPU speed. For a task that takes 5 seconds with two
> workstations online, if it take 10 seconds it's either CPU or HD
> access. If it takes 3 minutes, it's RAM ;-)

hmmm, got me thinking ... We have run variations of this capacity analysis thread a couple of times, and from several directions.

Assuming an otherwise properly configured host (DNS is a real killer when it is wrong), the major operative variables to watch (off the top of my head) are:

process load level -- how many processes are ready and waiting (i.e., not blocked), thread and handle depletion

swap thrashing -- how often is the system having to push stuff back and forth from swap

i/o blocking -- can the system get content from the drives ina timely fashion

network latencies -- collisions, aggregate bandwidth available actually in use

iostat, vmstat, netstat, ifconfig, procinfo, free, w, and the systat suite each watch parts of these items.

I will take a stab at setting up a cronnable tool for data collection, without major loading, in a form parsable by rrd or mrtg. SNMP collection is another route. The thought would be to produce a package to install, which gathers, and then yields a report which identifies the 'top offender' so that it can be addressed to a lay admin.

The stats also would permit a 'real' answer to the capacity analysis questions we see.

Also, there is a lot of prior art, and I see no need to reinvent the wheel. RRD seems like an early leader, but it is somewhat 'touchy feely' pictures. OpenNMS is too young, and somewhat dificult to get running.

Does anyone else have any favorite metrics to include on that list? A missing low level data collection, or end user presentation tool?

-- Russ Herrold

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