Hi Hoan,
what do you mean by "disk based"? The most fundamental idea of the datastore is that it runs from main memory, not disk. This is more than just an accident or a deficiency, it is a feature. If what you want is a O/R-mapping database layer, BKNR may serve as a starting point on how to interface to CLOS, not much more.
But maybe I am missing what you mean by "disk based". Can you explain?
-Hans