RE host checks configuration question

[Cyrille Bollu]

OK, I have find the explanation as what means a "check_interval" being set 
to 0 in the documentation of Nagios 3 (we are using 2.9 here): 0 means 
*regular* host checks are not performed. Which is good.

I have another question now: Are on-demand host checks scheduled when a 
service transits in a *soft* not-OK state or when it transits in a *hard* 
not-ok state?

This is a quite important question since knowing the answer to this 
question will influence the value I'm gonna set for the host 
"max_check_attempts" parameter: When "on-demand host checks" are scheduled 
when a service transits in a *hard* not-OK state, I will set the host 
"max_check_attempts" to a lower value than when "on-demand host checks" 
are scheduled when a service transits in a *hard* not-OK state (since I'm 
more confident in the service check result).

Also, there is something else not very clear in Nagios 3 documentation:

(from http://nagios.sourceforge.net/docs/3_0/hostchecks.html)
"Hosts which have their max_check_attempts value set to 1 can cause 
serious performance problems. The reason? If Nagios needs to determine 
their true state using the network reachability logic (to see if they're 
DOWN or UNREACHABLE), it will have to launch serial checks of all of the 
host's immediate parents. Just to reiterate, those checks are run serially
, rather than in parallel, so it can cause a big performance hit. For this 
reason, I would recommend that you always use a value greater than 1 for 
the max_check_attempts directives in your host definitions."

Well, I believe the writer of this documentation but I don't understand 
why setting this parameter to 1 will serialize the host's parents checks. 
Can someone explain me this point?

Best regards,

Cyrille

> 
> Hi all, 
> 
> My host checks are configured as follow: 
> 
> Host Name        Max. Check Attempts        Check Interval 
> Host Check Command        Enable Active Checks         Enable 
> Passive Checks         Check Freshness 
> adabase         5                         0h 0m 0s check-host-alive
> No                        Yes                                No 
> 
> Does this means that whenever a host check is needed, Nagios may 
> execute the "check-host-alive" command 5 times before a notification
> is sent? Wow, wouldn't be that bad?! 
> 
> And what does the "check interval" of 0 means? Might it take 5 
> minutes to get the notification? Should I set this parameter to "1min"? 
> 
> Could you help me? 
> 
> Best regards, 
> 
> Cyrille
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