Severe peformance issue during major network outage

[Ton Voon]

On 11 May 2007, at 19:03, Jim Avery wrote:

> On 11/05/07, Aidan Anderson <mail at aidananderson.co.uk> wrote:
>
>> A lot of people have mentioned using fping to speed things up but  
>> if my
>> average service latency is only 0.479 seconds in normal  
>> circumstances, I
>> can't see how tweaking this will help in a major outage situation.
>
> check_ping won't finish until it's done all the pings, and the pings
> are (if I recall) always at one second intervals.  This means that if
> you've configured check_ping to do (let's say) 5 pings, the check_ping
> plugin will always take at least 5 seconds to complete.
>
> If the check_ping is being run as a host check rather than a service
> check, my understanding is that this is the only thing Nagios will be
> doing; it doesn't do anything else concurrently (correct me if I'm
> wrong people).

Correct. We noticed this some time ago too: http://altinity.blogs.com/ 
dotorg/2006/05/immediate_perfo.html

If you do stick to using check_ping, use -p 1 which is sub second  
response time.


> In normal operation, nagios will rarely do a host check, as it only
> usually bothers to if all of the service checks (which can run
> concurrently) for that host have failed.  When lots of hosts go down
> at once, you suddenly notice how bad it is to have such slow host
> checks.

Nagios 3 will do parallelised host checks, so there will not be a  
slow down there.

Also, Ethan said in his presentation at the Netways conference last  
year that some of the host unreachable logic was not quite right:  
http://www.netways.de/uploads/media/Ethan.Galstad_Nagios. 
3.and.Beyond.pdf

This should be fixed in Nagios 3.

Ton

http://www.altinity.com
T: +44 (0)870 787 9243
F: +44 (0)845 280 1725
Skype: tonvoon



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