Antwort: Re: Antwort: Re: Fwd: plugin for iostat readings?

[Sascha.Runschke at gfkl.com]

Mike Hamrick <mikeh at bluegecko.net> schrieb am 02.03.2008 14:13:51:

> > You need to call iostat with multiple checks - the longer the better -
> > but then it means you would have to run iostat for like 30 seconds or
> > so -> plugin runtime is 30 seconds too then! That means that check
> > would have a high delay/latency, which is overall a bad idea. My
> > solution so far is to run the plugin via cron and report output via
> > nsca, this gave me the best results.
> 
> One thing you might want to consider is using sadc/sar for this job.
> The sadc(8) program collects all kinds of stats on OS resource usage
> and if you explicitly ask it, it will capture some interesting
> disk i/o stats, including read/write requests per second.

I actually have considered this, but found sadc not feasable for
my intents. I am not interested in general iowait, but more in
bandwidth usage of actual devices. Most of our high load servers
have 3 SAN connections and it's important to know _which_ of those
is under high stress and especially the performance data of
those statistics to determine upcoming problems.

At least I haven't been able to get sadc to log bandwitdh and
throughput for each block device individually. sar in interactive
mode is capable of doing it via "sar -dp 60 1" for example.

Another problem that arises when using sadc is the problem that
the scheduling of nagios is non predictable. I cannot garantuee,
that nagios will poll the information once a minute for example.
I cannot garantuee that nagios won't run the check twice in a
longer checkperiod. The biggest feature of using it via send_ncsa
passive checks, is the fact that I can inject the data when I want
to - with perfect timing.

But when using sar interactively, it's basically just a iostat -dp,
which does the average calculation at the end - something my plugin
already does ;)

I'll put out our options in an abstract way:

a) using sadc/sar:

Have $script run by cronjob.
Run active checks from nagios.

b) using my passive plugin.

Have $script run by cronjob.
Let $script send output to nagios.


In my opinion b) sound more appealing to me, since we have full
control of timings. I do not see any benefit of using a).

But maybe I am missing something - I am open to suggestions and
ideas ;)

S

PS: Please do not CC me, I don't like dupes ;)

-- 
Sascha Runschke
Netzwerk-  und  Systemmanagement        -       Abt. Organisation und 
Betrieb - IT-Infrastruktur
Telefon : +49 (201) 102-1879    Mobil : +49 (173) 5419665       Fax : +49 
(201) 102-1102105



GFKL Financial Services AG
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