Hello all!

I have an rrd collecting meteorological data. It has a step of 300 seconds and 
data is fairly reliably entered every 150 seconds. There are times when my 
computer is off and no data is entered. Explicit U's would be entered if there 
was a problem getting the data, but I haven't encountered that yet. The strange 
thing is that I have been getting these big, unexplained jumps in the graphs 
(with corresponding strange numbers in the rrd dump) after blank periods. The 
parameter in question (it happens to the others sometimes, but for some reason 
this last time it only manifested in this one) is the atmospheric pressure. It 
is stored as a GAUGE with a heartbeat of 600, a min of 0 and a max of U. I've 
got some RRA's, namely Average, Min, and Max at xff 0.1, 1 data point, and 7340 
rows (30 days of data i think); and xff 0.5, 12 data points, and 44040 rows (5 
years of data). I'm currently plotting the last 24 hours of data with a 
resolution of one pixel per data point. Before the blan
 k occurred, my script was writing 1015.8 into the pressure. Once the computer 
came back up, it was entering 1012.8 and 1012.4 (a bit of sensor noise between 
measurements i suppose). At no point did i write a 1008.9 or whatever its 
plotting there. Here is the offending graph output:

http://russkey.tumblr.com/post/4971101013/jumping-rrdtool

Any thoughts why this is happening? Anything I can do to stop it? I thought it 
might have something to do with the xff, so i changed it from 0.5 to 0.1 for 
the 1 data point per row RRA's but that doesn't seem to have helped. Though now 
that I think about it, perhaps it would make more sense to have just a single 
RRA for the 1 data point per row section, and have it a Last instead of an 
Average? Any help at all would be appreciated!

Al
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