[rrd-users] Max and Min logging.

Simon Hobson linux at thehobsons.co.uk
Wed Dec 24 14:45:02 CET 2008

I'm just setting up logging for the new UPS at work, and looking at 
teh SNMP MIB I see that it has entries for "The maximum utility line 
voltage in 0.1 VAC for last 1 minute." and "The minimum utility line 
voltage in 0.1 VAC for last 1 minute." as well as plain input 
voltage. I'm not really interested in logging voltage in small 
detail, but I would be interested in having max and min.

So if I were collecting data once a minute, and only graphing at 5 
minute resolution, is there an easy way to get the min and max values 
into the RRD ?

The only way I can think of is to set step to 1 (with suitably long 
heartbeat), and do 3 (or 4 ?) updates in close succession. Ie, do 
updates for t:act, t+1:min, and t+2:max (where act is current voltage 
reported, and min/max are the "min/max over last minute" reported by 
the UPS) to set the actual value for the last 58s, then the min and 
max for 1s each.

Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
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