The JRobinRrdStrategy was enhanced in version 1.8.5 to support the use of VDEFs (for e.g. calculating 95th percentile) in resource graphs on systems where JRobin is used to store RRD data. ML_cms reports via the IRC channel that the resource graph described at the following URL does not work for him in OpenNMS 1.8.7:
Investigation showed that the data sources (DEFs and CDEFs) needed to calculate a VDEF's value were not always being evaluated in the right order. This problem was due to the use of a HashMap in an operation sensitive to ordering. I've updated an existing unit test to illustrate the problem and have a fix ready to check in.