"Chris – I see you’re having some fun speculating over FAST implementation and strategies… I don’t think you’re really thinking this all the way through, though. The objective of promotion to a faster type of storage isn’t as simple as to try to stick the most recently requested data onto the fastest storage – heck – that would frequentrly be a waste of good Flash, because lots of data is accessed once and never again. No, the objective of FAST is to get the data that most often (and repeatedly) results in long response times when it requested over a period of time promoted – and to get that data promoted BEFORE it is even requested. Thus, the secret of FAST is to PREDICT what needs to be in Flash, and to determine what can safely be demoted to slower storage without significantly impacting response times – and then to get that data there at the right time. I can’t get into all the details here (patents and all that), but the simple LRU scheme you describe simply isn’t sufficient for..." - Barry Burke