[rrd-users] counting errors in rrd

Alex van den Bogaerdt alex at vandenbogaerdt.nl
Fri Mar 4 17:47:57 CET 2011

[I hope I'm not stating the obvious, just ignore me in that case]

> The ultimate goal in what I am doing is to show a graph of the response
> time, with our SLA times marked.  With outages in and out of SLA times
> (which is what I have setup now).

Everything is considered to be a rate. Remember that when you enter numbers. 
All numbers, no matter if you insert them as gauge, counter, end up as a 
rate internal to RRDtool.

I think you want to enter the duration of an outage in seconds.

With your goal, I think you will want to know especially the high numbers as 
it is the worst performance, so that when viewing a long period of time, say 
a whole year, you will notice the longest outage during a period of 86400 

>  The next step will be to figure out the
> total SLA availability and total avilability of the service that I am
> monitoring.  I was hoping to use the flags for this, realizing that it is
> not a true measure of uptime.  Checking every 5 mins, can show a 10 min
> outage, even though it was only down for the moment it took to do the 
> check.

For this, I think it would be best to have uptime as a fraction (or a 
percentage) of total time. Worst performance is the lowest number in this 

When entering uptime every 5 minutes, update it as a percentage or a 
fraction. RRDtool will then do the right thing for you when it is 
normalizing and consolidating. Computing how much of the previous 5 minutes 
your system was up is something you do outside RRDtool in this case.

When entering updates as system changes at specific (and known) time stamps, 
write a 1 (or 100) when the system goes from up to down, and a 0 when it 
goes from down to up. Make sure to have a high heartbeat setting, or 
periodically insert the current state even if there's no change.

have your downtime both as duration in seconds and as fraction of total 
time. Have MIN and MAX (and probably also AVERAGE) RRAs. 

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