[rrd-users] Re: New User Q's

[steve rader]

 > From: "S. William Schulz"
 > rrd update page.rrd \
 > 		946788901:75 \
 > 		946875300:2 \
 > 		946961700:31 \
 > 		947048100:8 \
 > [...]

...these are primary data points (PDPs.)

 >   946771200:           nan
 >   946857600:          2.00
 >   946944000:         25.06
 >   947030400:         12.71

...these are consolidated data points (CDPs).  They are the result of
"normalizing" your PDPs (at around 22:55 CST) so that they fit into
time slots (at around 18:00 CST) defined by your RRAs.

Third PDP sez there was an "average" 31 pages during Jan 3 22:55
through Jan 4 22:55 CST; whereas the third CDP above sez that there was
an average of 25.06 pages during Jan 3 18:00 through Jan 4 18:00 CST.

When your data is added at about 18:00 CST each day, the CDPs are
(better) "aligned" with your PDPs and thuse the data makes more
"sense":

  % more run_me

  rrdtool create page.rrd --start 946788900 --step 86400 \
    DS:pages:GAUGE:172800:0:1000 \
    RRA:AVERAGE:0.5:1:365

  rrdtool update page.rrd \
                946856600:75 \
                946943000:2 \
                947029400:31 \
                947115800:8 \
                947202200:31 

  % ./run_me
  % rrdtool fetch page.rrd AVERAGE -s 946857600 -e 947116800
                      pages

   946857600:         73.94
   946944000:          2.34
   947030400:         30.73
   947116800:          8.27

later
steve
- - -
systems guy
wiscnet.net

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