The underlying assumption, which I whole heartedly agree with, of
Joe Armstrong's algorithms is that any system that is scalable,
fault-tolerant, and upgradable is composed of
N nodes, where
N > 1.
The problem with current data storage systems, with
rare exception, is that
they are all "one box native" applications, i.e. from a world
N = 1. From Berkeley DB to MySQL, they were all designed
initially to sit on one box. Even after several years of dealing
with MegaData you still see painful stories like what the YouTube guys went through as they scaled up. All of this stems from
N = 1 mentality.