[rrd-users] rrd create update problem

[homephilsch at gmx.de]

Hi,

I want to create a rrd database that should be updated DAILY (86400 secs) by using unix crontab.

My problem is that the dump shows only NaNs.

This is my "rrdtool create" command:
timestamp=`date '+%s'`
rrdtool create a.rrd --start $timestamp --step 86400 DS:logRows:GAUGE:172800:0:U  RRA:AVERAGE:0.5:1:366 RRA:AVERAGE:0.5:7:53 RRA:AVERAGE:0.5:31:12

The "update command":
timestamp=`expr $timestamp + 1`
rrdtool update a.rrd $timestamp:175

Note: I set the "$timestamp+1" because otherwise the update command would claim that I cannot update the database with the same timestamp as the creation timestamp. Also note that the script creates a new database only if it did not already exist.

The result of "rrdtool dump a.rrd":
<!-- Round Robin Database Dump --><rrd> <version> 0003 </version>
        <step> 86400 </step> <!-- Seconds -->
        <lastupdate> 1280010602 </lastupdate> <!-- 2010-07-25 00:30:02 CEST -->

        <ds>
                <name> logRows </name>
                <type> GAUGE </type>
                <minimal_heartbeat> 172800 </minimal_heartbeat>
                <min> 0.0000000000e+00 </min>
                <max> NaN </max>

                <!-- PDP Status -->
                <last_ds> 175 </last_ds>
                <value> 1.7500000000e+02 </value>
                <unknown_sec> 81001 </unknown_sec>
        </ds>

<!-- Round Robin Archives -->   <rra>
                <cf> AVERAGE </cf>
                <pdp_per_row> 1 </pdp_per_row> <!-- 86400 seconds -->

                <params>
                <xff> 5.0000000000e-01 </xff>
                </params>
                <cdp_prep>
                        <ds>
                        <primary_value> 0.0000000000e+00 </primary_value>
                        <secondary_value> 0.0000000000e+00 </secondary_value>
                        <value> NaN </value>
                        <unknown_datapoints> 0 </unknown_datapoints>
                        </ds>
                </cdp_prep>
                <database>
                        <!-- 2009-07-24 02:00:00 CEST / 1248393600 --> <row><v> NaN </v></row>
                        <!-- 2009-07-25 02:00:00 CEST / 1248480000 --> <row><v> NaN </v></row>
                        <!-- 2009-07-26 02:00:00 CEST / 1248566400 --> <row><v> NaN </v></row>
                        <!-- 2009-07-27 02:00:00 CEST / 1248652800 --> <row><v> NaN </v></row>
                        <!-- 2009-07-28 02:00:00 CEST / 1248739200 --> <row><v> NaN </v></row>
                        <!-- 2009-07-29 02:00:00 CEST / 1248825600 --> <row><v> NaN </v></row>
                        <!-- 2009-07-30 02:00:00 CEST / 1248912000 --> <row><v> NaN </v></row>
                        <!-- 2009-07-31 02:00:00 CEST / 1248998400 --> <row><v> NaN </v></row>
                        <!-- 2009-08-01 02:00:00 CEST / 1249084800 --> <row><v> NaN </v></row>
.
.
.

My crontab entry:
30 0 * * * updateRRD.sh


As you can see the crontab runs successfully (see lastupdate).
So my question is why I have only NaNs in the dump? Why the start time is at 02:00:00 (is the difference caused by the UTC-CEST difference )? Is it correct to have the heartbeat set to 172800 or should I set it to a smaller number?

I read many tutorials on the web about the rrdtool but I could not figure out why my rrd database isn't updated correctly.

Note also that with a database of step rate 300 (as in the rrdtool tutorial my database is updated correctly).
For completeness: I use RRDtool 1.2.30


Your help is very appreciated.
Phil
-- 
Neu: GMX De-Mail - Einfach wie E-Mail, sicher wie ein Brief!  
Jetzt De-Mail-Adresse reservieren: http://portal.gmx.net/de/go/demail