[rrd-users] RRD files with more than one data source

Yishai Hadas Yishai.Hadas at aladdin.com
Mon Aug 27 11:37:09 CEST 2007

Hi List,


I'm new to RRDtool and have some basic questions about organizing RRD



>From looking at the documentation and the code it seems that both update
and graph (uses internally fetch) commands always use explicitly or
implicitly all DS defined in a given RRD file.


When using update it seems that even if <-template> option is used -
still unknown value is set to any non mentioned DS. 

When fetch is used there is no way in the API to relate to a specific DS
and all are fetched.


If I'm correct:

It seems reasonable to put some DS in same RRD file just if those DS are
really updated together and may be used together to build graphs.

Otherwise to use different RRD files - Each RRD file per DS.



But on the other hand:

What about disk space when many files are used?

What about performance as each update requires open and closes the file
- while bulk update of different DS in same RRD file can be done in one
update call?


My questions:


Am I correct in my understanding the APIs?

Is it recommended to define some DS on same RRD file? 

If yes when it's recommended?



Any help is appreciated.









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