[rrd-users] Data Source Name - 19 character limitation

Clint Cronwright - Jacarta Clint.Cronwright at jacarta.co.uk
Wed Nov 21 11:44:37 CET 2007


Thank you for the reply, I have passed this on and I now have more detail of
what is happening, can you please have a look at this and let me know if you
a suggestion to where this is going wrong.

What the problem is that for trending purposes, Midguard uses the RRD OID
number and the Element Name (DS Name) from the MIBs in order for it to work.

When I create our Jchecks, I upload them to the client's Midguard system and
using the RRD function, the RRDDaemon updates the data in its database and
also creates a rrd file (which has data points in them) which RRDTool uses
to draw and plots the charts.

Normally, Midguard doesn't have a problem updating its database and creating
the RRD files its needs to draw the charts. However, looking through the RRD
database, which has an error counter next to each entry (should always be 0
is there is no problem), the error counter next to the interSeptor
temperature and humidity RRD entry is very high.

Doing some investigation with our development team, we found out that all
the entries in the database that has an element name shorter or equal to 19
characters, the error counter is 0. Any element name entry that has more
that 19 characters in its element name, its has a high error counter value
next to it meaning that Midguard can not add or create the RRD files that is

Therefore, we concluded and looking through the internet that RRDTool has a
19 characters element name restriction (from
http://forums.cacti.net/post-385.html). Any more characters than 19 in the
element name, the error counter goes up.

Many thanks,

-----Original Message-----
From: Fabien Wernli [mailto:wernli at in2p3.fr] 
Sent: 21 November 2007 08:38
To: Clint Cronwright - Jacarta
Cc: rrd-users at lists.oetiker.ch
Subject: Re: [rrd-users] Data Source Name - 19 character limitation

On Tue, Nov 20, 2007 at 05:06:19PM -0000, Clint Cronwright - Jacarta wrote:
> The reason I ask is that I support an SNMP device, this device has some
> long element names within the MIB, 30+ characters, and I am being told
> this can not be used with RRDTool as the Data Source Names can only be 19
> characters long.

DSs in rrdtool can be whatever you like them to be. The names stored in the
RRD file are the ones you choose when creating it. The application gathering
the values and pushing them to rrdupdate just need to be in the same order
(if you don't specify templates).

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