Have searched, but not found an answer.
Presently running RRDTool at the same processor which is collecting the information, making rrd-files and related graphic output at that processor.
Is it also possible to run RRDTool at a server for graphic output, applying rrd-files being uploaded?
Yes; at least to some extent. You need to run rrdcached on your backend server; then, your collector and graphing servers can make remote calls to obtain or store the data.
How you tune rrdcached depends on the amount of data and frequency of writes, and how much you can afford to lose in the even of a server crash; however generally a 30min cache works. This also greatly decreases the amount of disk IO required.
Note that some rrdtool functions do not work exactly the same via rrdcached; check the documentation for more details.
Read about rrdcached here: https://oss.oetiker.ch/rrdtool/doc/rrdcached.en.html
