[rrd-users] Re: Help creating database

[BAARDA, Don]

G'day,

> -----Original Message-----
> From:	Rainer.Bawidamann at rz.uni-ulm.de
> [SMTP:Rainer.Bawidamann at rz.uni-ulm.de]
> Sent:	Tuesday, January 02, 2001 10:48 PM
> To:	rrd-users at list.ee.ethz.ch
> Subject:	[rrd-users] Re: Help creating database
> 
	[...]
> The 600 is the value for 'heartbeat'. From rrdcreate(1):
> 
>    heartbeat defines the maximum number of
>    seconds that may pass between two updates of
>    this data source before the value of the data
>    source is assumed to be *UNKNOWN*.
> 
> Make heartbeat allways bigger than step, maybe 4000 in this case.
> 
> (Maybe rrdtool shouldn't accept heartbeat settings lower than step?)
> 
	There are some admittedly very strange reasons why having a
heartbeat less than step _might_ be desirable. RRD will correctly accumulate
multiple samples into one PDP if you want it to, so you can force it to
require multiple samples per PDP if you want. For example, with a heartbeat
1/4 the size of step and xff of 0.5, you typically want 4 samples per PDP,
but as long as at least half  the PDP interval (typically at least two
samples) is not "unknown", the PDP will not be marked "unknown". 

	However, this sort of "oversampling" is of dubious value. It can be
used to get more accurate PDP's, but it is probably better to just use a
smaller step and accumulate to an RRA. I wouldn't like rrd to reject a
heartbeat less than step, but outputting a warning during "create" wouldn't
hurt (apart from bloat maybe).

> Rainer
> 
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