Right now, flash memory-based solid state drives are still more expensive than traditional disk drives in terms of the cost per gigabyte. But flash-based drives or some type of hybrid that combines both flash and traditional disk drives seem to be coming.
There have been a lot of talks about the potential impact of flash memory in general. But I have always wondered what kind of impact these flash-based drives may have on the database systems in particular. Note that in all the major commercial database management systems (I deleted the word relational between commercial and database in this sentence :-), a significant chunk of code and a significant amount of investment is devoted to trading many small random I/Os for fewer large sequential I/Os. So intuitively, flash memory with its different I/O performance characteristics could have a huge potential impact on this trade-off at least.
Recently, Goetz Graefe wrote an update on Gray and Putzolo's original five-minute rule. Graefe's paper is titled, "The Five-minute rule twenty years later, and how flash memory changes the rules".
What most intrigued me in this paper is not the impact on the five-minute rule itself, but rather the potential impact on the database system architecture. Overall, Graefe suggests that database systems use flash memory as persistent storage instead of transient memory. In addition, he argues that using flash memory as part of persistent storage will have an impact on database checkpoint performance, selection of page sizes, buffer management, space allocation, and some of the B-tree logic.