I think that a better use of the file system would yield much more performance, since JVM IO is pretty much optimized for file access anyway (and uses OS-level caching).
Makes sense to me: from what I understand of the issue the store is (mostly?) not updatable (you either do a write or a read)? If so you don't need a database; file systems are actually very efficient for that kind of thing...
I don't understand why you're using Jisp, either. It would seemt o be very slow for your needs, forcing things to be serialized in and out of a datastore.
When I've written cache system, I've always used the file system directly. The only catch is that some operating systems limit the number of files on disk or in a directory; a very active server could hit those limits using individual files.
..Scott
-- Scott Robert Ladd Coyote Gulch Productions (http://www.coyotegulch.com) Software Invention for High-Performance Computing
