I have collect runnings which puts performancedate like cpu usage oder network bandwith into rrd files.
My problem is, that i have a single file for each node in the cluster.
How can I get an overview graph for my Cluster?
(for example I have 5 nodes which send each 10Mbit, so the graph schould show 50Mbit)
You just specify each file for the DEF: section of rrdtool. See below for a hacky one-off I did as an example. Notice that one of them is foo_kbrandt_foo1 and the other is foo_kbrandt_foo2. So the graph is pulling from two different rrd files.