Originally written and maintained by Tim Conrad, vmstats is now being maintained on Github.
vmstats connects up to vCenter and retrieves stats for all the servers it is hosting - stats like cpu utilization, memory, disk io, etc. It then takes those stats and sends them over to Graphite which further processes them, and stores them.
We are working on getting it to send stats from our infrastructure that has over 6,000 vm's. It is slow going, but we are getting closer. We are testing it with ~3,000 vm's + esx's and are sending over 1.5 million stats every 20 seconds.
The back-end for the stats collection is using cyanite (with cassandra and elastic search), and the front-end is grafana.
I am trying my best to keep the changes small, but a rewrite would be very nice.