I wonder about this concept. The reality is that having enough RAM to power NASDAQ, and then being able to accurately reproduce the state of the data following a crash based on input being kept in a durable store - which effectively is IO to the disk, which is the same as, well, just writing to a DB to begin with.

Of course, Fowler talks about 'snapshotting' the data, which, again, makes me wonder if playing with all of this resident memory and the systems needed to make that happen haven't already been solved by...um...databases.