Job Config History plugin saves copy of cluster stats plugin data for each change in it. (around every minute)
Each copy of global-build-stats.xml takes about 10 Mb for my jenkins setup, so after few days of using both of pointed plugins "configuration history" took about 20 Gb of space.
Solution for this issue is to add "cluster-stats" into "system configuration exclude file pattern" in Job Config History configuration (http://JENKINS/configure).
It would also be nice to describe this issue on Cluster Stats/Job Config History plugins wiki.