I was actually thinking of a >2GB DB file on a 32 bit server. But leaving that aside, it sounds like you're assuming a perfect hash function with no collisions.

I was actually thinking of a >2GB DB file on a 32 bit server. But leaving that aside, it sounds like you're assuming a perfect hash function with no collisions. If you have collisions, you have to deal with the possibility of a hash bucket overflowing and requiring an additional seek. Anyway, I don't doubt that you can operate in 2 seeks in the normal case.