[rrd-users] step period, start and end

Simon Hobson linux at thehobsons.co.uk
Wed Sep 22 18:16:53 CEST 2010

Justin Carroll wrote:

>It does make sense that everything would be related to UTC.  I don't 
>really want to fudge the time zone info here and you mentioned "If 
>you want a period other than that you will need to keep a more 
>detailed set of data and do things slightly differently."  Please 

For example, instead of having a consolidation period of one day - 
which only covers midnight to midnight UTC - you might keep data for 
each hour. That way, you can ask for a graph from midnight to 
midnight local time, which might be 6am to 6am UTC.

>Also, if a data source is GAUGE then "These are "real" values so 
>they should match what we put in" the rrd.  If the source of data is 
>an accumulation ie. total number of cars past a certain point with 
>respect to time, then the data will reflect just that.  In this 
>particular case I am not measuring rate.

But RRD never stores anything but a rate<period>. Even when you use a 
guage type, it still converts to a rate internally. Unless you are 
very careful with your updates, normalisation will mean that the 
values you enter will not be what's stored in the database.
See Alex's tutorial on normalisation and consolidation at 

Simon Hobson

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