title: rrd updated with NaN
body: <p>I'm trying to update an rrd file with new data every 10 minutes. I've got a cronjob set to run every 10 minutes that should run the update command, but when I dump the contents of the rrd file afterwards, all values show up as NaN. </p>
  
  <p>I've looked at a lot of different sites that indicate it's probably a problem with timing/step/heartbeat. I've fiddled with these and still can't get any values to show up. </p>
  
  <p>Right now my step size is 600 and the heartbeat is 900 and the wrapper script runs every 10 minutes (600). This code is part of a function that will be called a couple times to create a couple of databases, hence the DSBOGO to keep it general.</p>
  
  <pre><code>$cmdCommand .= "DS:DSBOGO:GAUGE:900:U:U \\";
  $cmdCommand .= "RRA:AVERAGE:0.5:1:720000 \\";
  $cmdCommand .= "RRA:AVERAGE:0.5:5:144000 \\";
  $cmdCommand .= "RRA:AVERAGE:0.5:60:12000 \\";
  $cmdCommand .= "RRA:AVERAGE:0.5:240:3000";
  </code></pre>
  
  <p>Below is the rrdtool info output</p>
  
  <pre><code>filename = "TEMPNAMERcvd.rrd"
  rrd_version = "0003"
  step = 600
  last_update = 631200000
  ds[DSBOGO].type = "GAUGE"
  ds[DSBOGO].minimal_heartbeat = 900
  ds[DSBOGO].min = NaN
  ds[DSBOGO].max = NaN
  ds[DSBOGO].last_ds = "UNKN"
  ds[DSBOGO].value = 0.0000000000e+00
  ds[DSBOGO].unknown_sec = 0
  rra[0].cf = "AVERAGE"
  rra[0].rows = 720000
  rra[0].pdp_per_row = 1
  rra[0].xff = 5.0000000000e-01
  rra[0].cdp_prep[0].value = NaN
  rra[0].cdp_prep[0].unknown_datapoints = 0
  rra[1].cf = "AVERAGE"
  rra[1].rows = 144000
  rra[1].pdp_per_row = 5
  rra[1].xff = 5.0000000000e-01
  rra[1].cdp_prep[0].value = NaN
  rra[1].cdp_prep[0].unknown_datapoints = 0
  rra[2].cf = "AVERAGE"
  rra[2].rows = 12000
  rra[2].pdp_per_row = 60
  rra[2].xff = 5.0000000000e-01
  rra[2].cdp_prep[0].value = NaN
  rra[2].cdp_prep[0].unknown_datapoints = 20
  rra[3].cf = "AVERAGE"
  rra[3].rows = 3000
  rra[3].pdp_per_row = 240
  rra[3].xff = 5.0000000000e-01
  rra[3].cdp_prep[0].value = NaN
  rra[3].cdp_prep[0].unknown_datapoints = 80
  </code></pre>
  
  <p>And here is a sample of the rrdtool dump output sample</p>
  
  <pre><code>&lt;!-- Round Robin Database Dump --&gt;&lt;rrd&gt; &lt;version&gt; 0003 &lt;/version&gt;
          &lt;step&gt; 600 &lt;/step&gt; &lt;!-- Seconds --&gt;
          &lt;lastupdate&gt; 1470334800 &lt;/lastupdate&gt; &lt;!-- 2016-08-04 14:20:00 EDT --&gt;
  
          &lt;ds&gt;
                  &lt;name&gt; DSBOGO &lt;/name&gt;
                  &lt;type&gt; GAUGE &lt;/type&gt;
                  &lt;minimal_heartbeat&gt; 900 &lt;/minimal_heartbeat&gt;
                  &lt;min&gt; NaN &lt;/min&gt;
                  &lt;max&gt; NaN &lt;/max&gt;
  
                  &lt;!-- PDP Status --&gt;
                  &lt;last_ds&gt; 0 &lt;/last_ds&gt;
                  &lt;value&gt; NaN &lt;/value&gt;
                  &lt;unknown_sec&gt; 0 &lt;/unknown_sec&gt;
          &lt;/ds&gt;
  
  &lt;!-- Round Robin Archives --&gt;   &lt;rra&gt;
                  &lt;cf&gt; AVERAGE &lt;/cf&gt;
                  &lt;pdp_per_row&gt; 1 &lt;/pdp_per_row&gt; &lt;!-- 600 seconds --&gt;
  
                  &lt;params&gt;
                  &lt;xff&gt; 5.0000000000e-01 &lt;/xff&gt;
                  &lt;/params&gt;
                  &lt;cdp_prep&gt;
                          &lt;ds&gt;
                          &lt;primary_value&gt; NaN &lt;/primary_value&gt;
                          &lt;secondary_value&gt; NaN &lt;/secondary_value&gt;
                          &lt;value&gt; NaN &lt;/value&gt;
                          &lt;unknown_datapoints&gt; 0 &lt;/unknown_datapoints&gt;
                          &lt;/ds&gt;
                  &lt;/cdp_prep&gt;
  
                  &lt;database&gt;
                          &lt;!-- 2016-05-01 00:00:00 EDT / 1462075200 --&gt; &lt;row&gt;&lt;v&gt; NaN &lt;/v&gt;&lt;/row&gt;
                          &lt;!-- 2016-05-01 00:10:00 EDT / 1462075800 --&gt; &lt;row&gt;&lt;v&gt; NaN &lt;/v&gt;&lt;/row&gt;
                          &lt;!-- 2016-05-01 00:20:00 EDT / 1462076400 --&gt; &lt;row&gt;&lt;v&gt; NaN &lt;/v&gt;&lt;/row&gt;
                          &lt;!-- 2016-05-01 00:30:00 EDT / 1462077000 --&gt; &lt;row&gt;&lt;v&gt; NaN &lt;/v&gt;&lt;/row&gt;
                          &lt;!-- 2016-05-01 00:40:00 EDT / 1462077600 --&gt; &lt;row&gt;&lt;v&gt; NaN &lt;/v&gt;&lt;/row&gt;
                          &lt;!-- 2016-05-01 00:50:00 EDT / 1462078200 --&gt; &lt;row&gt;&lt;v&gt; NaN &lt;/v&gt;&lt;/row&gt;
                          &lt;!-- 2016-05-01 01:00:00 EDT / 1462078800 --&gt; &lt;row&gt;&lt;v&gt; NaN &lt;/v&gt;&lt;/row&gt;
                          &lt;!-- 2016-05-01 01:10:00 EDT / 1462079400 --&gt; &lt;row&gt;&lt;v&gt; NaN &lt;/v&gt;&lt;/row&gt;
                          &lt;!-- 2016-05-01 01:20:00 EDT / 1462080000 --&gt; &lt;row&gt;&lt;v&gt; NaN &lt;/v&gt;&lt;/row&gt;
                          &lt;!-- 2016-05-01 01:30:00 EDT / 1462080600 --&gt; &lt;row&gt;&lt;v&gt; NaN &lt;/v&gt;&lt;/row&gt;
                          &lt;!-- 2016-05-01 01:40:00 EDT / 1462081200 --&gt; &lt;row&gt;&lt;v&gt; NaN &lt;/v&gt;&lt;/row&gt;
                          &lt;!-- 2016-05-01 01:50:00 EDT / 1462081800 --&gt; &lt;row&gt;&lt;v&gt; NaN &lt;/v&gt;&lt;/row&gt;
                          &lt;!-- 2016-05-01 02:00:00 EDT / 1462082400 --&gt; &lt;row&gt;&lt;v&gt; NaN &lt;/v&gt;&lt;/row&gt;
  </code></pre>
  
  <p>It seems like all of my timing parameters are set up correctly, but I cannot get this to work. I've let it run for over an hour now, and no data has shown up. Not sure what else to try at this point.</p>
  
  <p>I went through the whole script again printing out all of the outputs and discovered the data was not updating as often as I expected. I increased the heartbeat size and started getting data. </p>