[mrtg] Re: Problem with past data after disaster recovery

Peter Glanville peter_glanville at cuk.canon.co.uk
Tue Jul 13 10:28:04 MEST 2004

>Hi all,
> I'm facing a big problem with mrtg right now. Last week, my mrtg
>server's HD just crashed, and I had to restore a backup. As a result,
>mrtg losts about 1 day of data, and the grafic of that day becomes a
>straight line (as explained in the FAQ).
>My problem is that mrtg seemed to recalculate all its past data, and the
>values before the crash day became extremely low. Looking at the grafic,
>you can see clearly the division between 'before' and 'after' the crash
>and, because the autoscalling, you can't even see the values before the
>crash event (they appear to be 'zeros').
> How can I solve this? Can I just copy the values from the day before
>the crash (for example) to the day with missing data?

Your data has not been recalculated or corrupted.
Normal traffic has high spikes, but the 24-hour average is much lower
When no data is plotted, MRTG may assume a flat line at the last known 
value (which may have been mid-spike)
The average for the day of a high level flat line, is a high level data 
That causes the graph to auto scale and everything else seems low by 

A possible cure for the future is to use UnknownAsZero. But there are some 
reasons not to use that. Your choice.

If you use Rateup, I suppose it would be possible to edit the Log file, 
and remove the high daily value.
If you use RRD, then it is vaguely possible that Killspike.pl may knock 
out the high day. It's good for taking out erroneous spikes after re-boots 
etc, but not certain how it would handle your issue.


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