[rrd-users] Adding a new ds to an existing rrd

Marc Haber mh+rrd-users at zugschlus.de
Fri Aug 19 11:22:50 MEST 2005


I need to add a ds to an existing rrd, and would like doing so without
losing all history data for the other ds's in the rrd file. This seems
to be harder than I expected.

rrdtool info prints the rrd information in a completely different
format than rrdtool create wants to see it. It would be so nice to
have rrdtool info print something that can easily be amended with the
missing DS line and then pasted to an rrdtool create line.

Besides the output format, rrdtool info only prints the timestamp of
last update, while rrdtool create expects the timestamp of the
first data point. Maybe that timestamp can be calculated from the
last_update and the rra information, but I didn't yet try to figure
this out. rrdtool has the information (timestamp of the first data
point in the rrd) readily available, so it should give out that

rrdtool fetch does not seem to have an option "print all you have".
One needs, again, to guess or calculate the starting timestamp, and
then rrdtool will only print datapoints in the finest resolution that
is available for the entire period. When I rrdtool fetch from 1 to
now, I don't get the five minute resoltion data for the last 36 hours
which are available in the rrd. Thus, one has to finely analyze the
RRA data to find out what to ask rrdtool if one wants to pull all data
from the rrd.

Again, the output of rrdtool dump shows that rrdtool is able to print
every data point available automatically, but the XML format is hard
to parse. It would be so nice to get all data points in the same
format as rrdtool fetch prints (or RRDs fetch puts into perl data

Am I missing something, or is rrdtool really missing these useful

Or am I on the wrong way and it is easy to add a new DS to an existing
rrd doing it differently?

Any hints will be appreciated.


Marc Haber         | "I don't trust Computers. They | Mailadresse im Header
Mannheim, Germany  |  lose things."    Winona Ryder | Fon: *49 621 72739834
Nordisch by Nature |  How to make an American Quilt | Fax: *49 621 72739835

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