Relevant for your comment as well as others, RavenDB uses Esent as backend:
https://github.com/ravendb/ravendb/tree/master/Raven.Storage...
http://en.wikipedia.org/wiki/Extensible_Storage_Engine
http://trycatchfail.com/blog/post/Alternatives-to-Relational...
Notice "DivanDB" in the blogpost :).
so, there it is.