[rrd-users] Re: Limit on step size in rrdtool create?
Tobias Oetiker
oetiker at ee.ethz.ch
Thu Aug 12 16:30:55 MEST 1999
Today you sent me mail regarding [rrd-users] Limit on step size in rrdtool...:
*> I'm a new user to rrd and have rrdtool-1.0.4 on my Redhat 6 box.
*>
*> I'm interested in plotting one value per day, and thought I could just
*> set the step size to 86400 (seconds in a day) and use rrdtool update for
*> each new value. However, I found that the values I was putting in via
*> rrdtool update were not the the ones in the RRA. After playing around
*> with it a while, I found that things worked as I thought they should
*> work if the step size was 3600 seconds or less.
*>
*> Perhaps it is just my ignorance of how the tool saves data. Can someone
*> explain what is going on?
*>
*> I have 2 examples below. Both use the same start time (7 March 1999,
*> 5:00 AM CST). The first example has a step size of 3600 secs, the second
*> example 7200 secs. After I create the rrd, I update it with 5 values. In
*> the first example, I update it every 3600 seconds, in the second I
*> update it every 7200 seconds.
*>
*> A dump of the rrd for the first example shows what I would expect. Since
*> I updated the rrd every hour, starting an hour after the start time, the
*> values I put in show up in the rra.
*>
*> But in the dump from the second example, the times in the rra are 6:00,
*> 8:00, 10:00, 12:00, & 14:00. I would expect the times to be 7:00, 9:00,
*> 11:00, 13:00, and 15:00, since the start time was 5:00, and the step
*> size is 2 hours. Also, the values are obviously interpolated since the
*> times I specified in the update were 7:00, 9:00, 11:00, 13:00 and 15:00.
*> Is this the way it is supposed to work, and if so, why?
RRA timestamps are always at those points in time whare the number of
seconds since 1.1.1970 00:00 GMT module the chosen step size is zero
hope this helps
tobi
*>
*> Thanks
*> Gary
*>
*>
*>
*>
*> $ rrdtool create test.rrd --start 920804400 --step 3600
*> DS:speed:GAUGE:7200:U:U RRA:LAST:0.5:1:5
*> $ rrdtool update test.rrd 920808000:40
*> $ rrdtool update test.rrd 920811600:50
*> $ rrdtool update test.rrd 920815200:60
*> $ rrdtool update test.rrd 920818800:70
*> $ rrdtool update test.rrd 920822400:80
*>
*> $ rrdtool dump test.rrd
*> <!-- Round Robin Database Dump -->
*> <rrd>
*> <version> 0001 </version>
*> <step> 3600 </step> <!-- Seconds -->
*> <lastupdate> 920822400 </lastupdate> <!-- 1999-03-07 10:00:00 CST -->
*>
*> <ds>
*> <name> speed </name>
*> <type> GAUGE </type>
*> <minimal_heartbeat> 7200 </minimal_heartbeat>
*> <min> NaN </min>
*> <max> NaN </max>
*>
*> <!-- PDP Status -->
*> <last_ds> UNKN </last_ds>
*> <value> 0.0000000000e+00 </value>
*> <unknown_sec> 0 </unknown_sec>
*> </ds>
*>
*> <!-- Round Robin Archives -->
*> <rra>
*> <cf> LAST </cf>
*> <pdp_per_row> 1 </pdp_per_row> <!-- 3600 seconds -->
*>
*> <cdp_prep>
*> <ds><value> NaN </value> <unknown_datapoints> 0
*> </unknown_datapoints></ds>
*> </cdp_prep>
*> <database>
*> <!-- 1999-03-07 06:00:00 CST --> <row><v> 4.0000000000e+01 </v></row>
*> <!-- 1999-03-07 07:00:00 CST --> <row><v> 5.0000000000e+01 </v></row>
*> <!-- 1999-03-07 08:00:00 CST --> <row><v> 6.0000000000e+01 </v></row>
*> <!-- 1999-03-07 09:00:00 CST --> <row><v> 7.0000000000e+01 </v></row>
*> <!-- 1999-03-07 10:00:00 CST --> <row><v> 8.0000000000e+01 </v></row>
*> </database>
*> </rra>
*> </rrd>
*>
*>
*>
*> --------------------------------------------------
*>
*> $ rrdtool create test.rrd --start 920804400 --step 7200
*> DS:speed:GAUGE:14400:U:U RRA:LAST:0.5:1:5
*> $ rrdtool update test.rrd 920811600:40
*> $ rrdtool update test.rrd 920818800:50
*> $ rrdtool update test.rrd 920826000:60
*> $ rrdtool update test.rrd 920833200:70
*> $ rrdtool update test.rrd 920840400:80
*>
*> $ rrdtool dump test.rrd
*> <!-- Round Robin Database Dump -->
*> <rrd>
*> <version> 0001 </version>
*> <step> 7200 </step> <!-- Seconds -->
*> <lastupdate> 920840400 </lastupdate> <!-- 1999-03-07 15:00:00 CST -->
*>
*> <ds>
*> <name> speed </name>
*> <type> GAUGE </type>
*> <minimal_heartbeat> 14400 </minimal_heartbeat>
*> <min> NaN </min>
*> <max> NaN </max>
*>
*> <!-- PDP Status -->
*> <last_ds> UNKN </last_ds>
*> <value> 2.8800000000e+05 </value>
*> <unknown_sec> 0 </unknown_sec>
*> </ds>
*>
*> <!-- Round Robin Archives -->
*> <rra>
*> <cf> LAST </cf>
*> <pdp_per_row> 1 </pdp_per_row> <!-- 7200 seconds -->
*>
*> <cdp_prep>
*> <ds><value> NaN </value> <unknown_datapoints> 0
*> </unknown_datapoints></ds>
*> </cdp_prep>
*> <database>
*> <!-- 1999-03-07 06:00:00 CST --> <row><v> 4.0000000000e+01 </v></row>
*> <!-- 1999-03-07 08:00:00 CST --> <row><v> 4.5000000000e+01 </v></row>
*> <!-- 1999-03-07 10:00:00 CST --> <row><v> 5.5000000000e+01 </v></row>
*> <!-- 1999-03-07 12:00:00 CST --> <row><v> 6.5000000000e+01 </v></row>
*> <!-- 1999-03-07 14:00:00 CST --> <row><v> 7.5000000000e+01 </v></row>
*> </database>
*> </rra>
*> </rrd>
*>
*>
*>
*>
--
______ __ _
/_ __/_ / / (_) Oetiker, Timelord & SysMgr @ EE-Dept ETH-Zurich
/ // _ \/ _ \/ / TEL: +41(0)1-6325286 FAX:...1517 ICQ: 10419518
/_/ \.__/_.__/_/ oetiker at ee.ethz.ch http://ee-staff.ethz.ch/~oetiker
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