[rrd-users] Strange values in RRA

[Olivier Nicole]

Hi,

I use RRD::Simple to add new DS in an RRD.

I create the RRD with one DS:
        <ds>
                <name> tick </name>
                <type> GAUGE </type>
                <minimal_heartbeat>600</minimal_heartbeat>
                <min>0.0000000000e+00</min>
                <max>NaN</max>

                <!-- PDP Status -->
                <last_ds>1</last_ds>
                <value>1.0000000000e+00</value>
                <unknown_sec> 0 </unknown_sec>
        </ds>
and very standards RRA:
    'RRA:AVERAGE:0.5:1:600',
    'RRA:AVERAGE:0.5:6:600', 
    'RRA:AVERAGE:0.5:24:600', 
    'RRA:AVERAGE:0.5:288:732'

At each step, I enter the value 1 for DS "tick".

As time goes, I add new DSs.

--------

At 17:40 I add a new DS called "1":

        <ds>
                <name> 1 </name>
                <type> GAUGE </type>
                <minimal_heartbeat>600</minimal_heartbeat>
                <min>0.0000000000e+00</min>
                <max>NaN</max>

                <!-- PDP Status -->
                <last_ds>U</last_ds>
                <value>NaN</value>
                <unknown_sec> 1 </unknown_sec>
        </ds>

and I enter the value 1 for DS "1"; in the first RRA, I get:

<!-- 2012-11-22 17:40:00 ICT / 1353580800 --> 
    <row><v>1.0000000000e+00</v>
         <v>9.9666666667e-01</v></row>

--------

At 19:25 I add a new DS called "2":

        <ds>
                <name> 2 </name>
                <type> GAUGE </type>
                <minimal_heartbeat>600</minimal_heartbeat>
                <min>0.0000000000e+00</min>
                <max>NaN</max>

                <!-- PDP Status -->
                <last_ds>U</last_ds>
                <value>NaN</value>
                <unknown_sec> 1 </unknown_sec>
        </ds>

and I enter the value 1 for DS "1" and DS "2"; in the first RRA, I get:

<!-- 2012-11-22 19:25:00 ICT / 1353587100 --> 
    <row><v>1.0000000000e+00</v>
         <v>1.0000000000e+00</v>
         <v>9.9666666667e-01</v></row>

-------

So far so good.There is no other data entry. 

But when I look at the second RRA, I get:

<!-- 2012-11-22 19:30:00 ICT / 1353587400 --> 
    <row><v>1.0000000000e+00</v>
         <v>NaN</v>
         <v>1.9933333333e-01</v></row>


While I would be expecting something along the line of:

<!-- 2012-11-22 19:30:00 ICT / 1353587400 --> 
    <row><v>1.0000000000e+00</v>
         <v>1.6666666666e-01</v>
         <v>1.6666666666e-01</v></row>

as there have been only one entry of value 1 in DS "1" and DS "2" in
the past 6 steps.

It could be an artefact of RRD::Simple that seems not to be working so
well.

Help appreciated,

Best regards,

Olivier