[iambvk]

I am working on implement on-disk B+Tree for the last few months. Man, keeping the on-disk state consistent with proper locking is a real challenge -- specially when we want to avoid IO-holding-mutex. And forward/backward iterators make me doubt the correctness.

All this with just fixed size keys/values. I am yet to start on variable sized keys and values, but I already want to give up on my initial performance targets.