All I need is a large persistent lookup table in Erlang and dets seems like just the thing though I need a definative answer to:
One obvious approach, once it is thought of, is to hash dets entries over multiple dets files.
A linear hash should make it dynamically growable, by splitting buckets into newly created dets files when one file reaches an upper threshold.
There are also a number of port drivers that enable you to use sleepycat/berkely db, or tokyo tyrrant. Those databases have file limits that are much higher than 2Gb.