Quantifying the Flash Zone

This is quite the time for Flash-based solid-state drives (SSDs)! Seagate just dropped into the market and whenever a heavyweight like Seagate drops in, there’s a big splash. This announcement helped lead me into a discussion of the live (!) SSD seminar that distributor Bell Micro has just taken across North America. The road show landed in Milpitas earlier this month and the keynote speaker, storage analyst extraordinaire Jim Handy, did a great job of covering the topics of interest to server designers and enterprise system architects.

The Flash Zone is a concept described by Denali Software’s CTO Mark Gogolewski in his keynote speech—The World is Flash: A Disruption of the Memory & Storage Hierarchy—at Memcon 2009. The Flash Zone is the name put to the performance gap between DRAM and disk storage. There’s not only a gap in performance within the Flash Zone, there’s a transition from volatile memory (DRAM) to non-volatile storage (hard disk). With steep cost/bit price declines and per-device capacity growth, NAND Flash devices now easily fit into this gap and produce a new and viable layer in the overall computer memory hierarchy.

What’s new is that Jim Handy’s keynote at the Bell Micro SSD seminar put some welcome numbers on the Flash Zone that further clarify Flash’s place in the hierarchy. Here’s an image of that particular slide.

This image plots the performance and cost of the different memory hierarchy layers from first-, second-, and third-level processor cache through DRAM, disk, and tape. Because Handy’s used a log-log scale to plot everything, the graph looks nice and linear even though the reality is quite a bit messier. For a conceptual graph however, this’ll do nicely.

Note that there’s a gap in the hierarchy. That’s the Flash Zone. Here’s the same plot augmented a bit. The big red circle identifies the Flash Zone.

Also note that Handy has labeled the gap and says it’s “growing.” The gap’s growing because DRAM is getting faster, bigger, and cheaper, moving its ellipse up and to the left while HDDs are getting bigger, although not much faster, moving the HDD ellipse horizontally to the left. The result is a growing performance and bandwidth gap between DRAM and HDDs.

Flash fits into this gap very, very nicely said Handy (and as discussed in this blog). Later in his keynote, he displayed this image to underscore the point.

For more analysis of this subject, please see an extended version of this blog here.

Note: Handy’s keynote was based on his company’s new report: Solid State Drives in the Enterprise – 2010.