Counters that may reset

[unitron]

(cacti-0.8.6h)

I have a script which gets the total smtp in/out traffic from my mail servers. This is read into a 'COUNTER' data source then graphed.

Recently the mailstats were cleared and this caused cacti to report a huge value rather than the usual ~100 i expect per 5 minutes.
Having no method of clearing this one value meant I ended up scraping the rra file and starting again. Fortunately it only had around a day of data.

This itself is not a problem as I am under the impression i can use the 'mailstats -p' command which clears the stats on every request and store the data using the 'ABSOLUTE' data type. Is this correct?

The problem is, I want to graph the throughput of my web servers next.
These have a KB/s counter avilable which may be reset if the server needs restarting. I have no way of clearing these on each request.

Whats the correct way to store this information? I don't want to have to scrap months of data because the counter reset and caused a massive spike in the data.

[gandalf]

I would recommend setting a reasonable MAXIMUM limit for each of the data sources of your Data Template. All values exceeding this MAXIMUM will be clipped off when performing "rrdtool update". Existing rrd files will have to be tweaked using "rrdtool tune" to reset the MAXIMUM
Reinhard