The problem is exactly the one with VM: I believe that likely disk will suck but for a specific work load, that is, extremely biased working set + mostly reads.

The problem is exactly the one with VM: I believe that likely disk will suck but for a specific work load, that is, extremely biased working set + mostly reads. But this is exactly the use case of on disk DBs anyway, that are doing a lot work to work well in this use case, why should we also enter this business? There should be space for everybody, I'll be very happy if we'll do our work well, that is, the in memory data structure server :) BUT I did not stop experimenting, we'll return on this, but in the form of diskstore and as on disk allocators using mmap() that is another thing I'm playing with.