After having worked with Elasticsearch and thrown quite a lot of data at it (we add about 100 million documents a day), I have built a very nice set of graphs, that helps me visualize problems and activity in the cluster, and figured I'd share them to hopefully give some inspiration :)
p.s. the jvm_heap_usage graphs - the two lines which are very jumpy, are the ones I switched to using G1 Garbage Collector, which does seem to be of help when you're running close to your heap limit :)
p.s. view image alone, to see it in full size.