Flash vs disk at DISKCON 2007

by Robin Harris on Monday, 24 September, 2007

The tension was real
The disk guys acknowledged that flash has killed the sub-1.8″ drive market. Will 1.8″ drives be next?

The flash guys acknowledged that they have a huge economic problem: heavy seasonality of demand. Consumer demand drives a Q4 peak in flash sales. But what to do with a $5 billion flash factory the rest of the year? Look for other markets, that’s what.

The flash guys announced a goal of taking 25-28% of disk revenue for themselves.

Flash drives aren’t living up to the hype
Which is no big surprise. The divergence is simply getting more visible (see my ZDnet articles Hybrid drives: not so fast, Flash drives: your mileage WILL vary, and Power, notebooks and solid state disk).

WD strikes back
The most outspoken disk defender is Rich Rutledge, SVP at Western Digital, the 2nd largest disk manufacturer. His argument, which is overlong for consumers, is that flash will *never* deliver on the hype, because it can’t. Rich’s point is that flash’s advantages are largely illusory:

  • Power: disks are pretty efficient, and today’s notebooks have a lot of power-hogging systems (Wi-fi, Bluetooth, display, dual-core processors, GB of RAM and graphics co-processors) so the additional battery life that flash can deliver is less than 6%.
  • Boot times: cold boot not all that much faster – 8-10% – and the fastest boot times in Vista come from Vista’s Sleep mode, which uses the battery to keep your data live in RAM, the fastest mass storage you own.
  • Size & weight: important in handheld devices, but notebook size and weight are dominated by keyboard and screen requirements, not the extra grams of a disk drive. Flash in small ultra-light notebooks? Sure. In a 17″ behemoth? Much less likely.
  • Performance: flash, is an unlimited dragster – fast in the quarter mile, but no good on curves. That is, the flash drive’s massive advantage in small random read speed is lost in the real world where small random writes and large sequential reads and writes drown out the flash drive’s one big performance advantage.

Rick had a larger point as well. The disk guys have an incredible story to tell and they aren’t telling it. I’ll be getting into some of that later this week.

Taking down the hype
About 20 years ago I took down a hype-fueled machine – Manufacturing Automation Protocol – that had large customer interest, seemingly unassailable technical advantages and major vendor support. And I had a blast doing it.

If the disk folks don’t tell their story they can’t expect anyone to do it for them.

The Storage Bits take
Rich makes some good points, but I’m not ready to write flash off. Let’s give the flash engineers a chance to work some magic. But I’m far from convinced that the flash vendors have the Mojo to pull off what they’ve promised. Enough hype, let’s see some results.

That said, I do believe that flash will own the low-end of the storage market such as handheld devices and ultra-light PCs where size, weight and power really are critical and capacity/performance much less so. 1.8″ drives are in the free-fire zone. They’ll hang in there, but only by driving capacity hard.

Hybrid drives are doomed. Relying on Microsoft to make a peripheral hardware product economically viable is weak. Plus spending a few bucks on DRAM which speeds everything up just makes more sense than spending that money on sometimes speeding up a disk.

Update: Barry Whyte, an IBM’er in the UK, sent me a link to his blog
where he discusses his test of the high-end STEC flash-based SSD behind an IBM controller. The money quote:

. . . the host was seeing close to 50,000 read ops and just shy of 19,000 write ops! Over 100MB/s and closer to 200MB/s with SVC’s sequential pre-fetch.

STEC was at DISKCON, and I tried to talk to one of their engineers, but it was not to be. Essentially they have a many parallel pipes to a lot of flash chips so they can do that many writes. I don’t share Barry’s confidence that STEC will be able to drive the price down as fast as NAND is going. That kind of engineering isn’t cheap and STEC will want their deserved 50%+ gross margins for their controller Mojo. End update.

Comments welcome, as always. Maybe someone out there understands the hybrid drive equation better than I do.

{ 7 comments… read them below or add one }

Barry Whyte Monday, 24 September, 2007 at 9:10 am
Hans Thursday, 27 September, 2007 at 9:42 am

Have you looked at the Fusion-IO PCI-e based flash card introduced in DEMO?
I am looking at them for possible use in VOD applcations..

Matt Friday, 28 September, 2007 at 5:13 am

Hans,

Why would you need flash for VOD (I take it you mean video on demand). Video is inherently disk friendly with its combination of very large files and large block sequential reads and writes. Outside of edge cases, flash is never going to be crazy useful in video.

Or are you doing something strange?

Hans Friday, 28 September, 2007 at 10:00 am

It’s the number of concurrent streams….

Bill Todd Tuesday, 2 October, 2007 at 3:30 am

The number of concurrent streams still simply boils down to aggregate storage bandwidth, and for large sequential (i.e., streaming) accesses commodity disks can provide that at less than 1/10th the price that the least expensive flash can. Even extreme hot spots where a large percentage of streams focus on a small percentage of files can be handled as long as the files are spread across the entire array, since the streams are staggered in the time dimension. And for pathologically intense access cases, data caching in server RAM can perform the same service as flash without the cost of keeping *everything* in expensive high-speed storage.

- bill

Amir Hermelin Monday, 22 October, 2007 at 3:54 pm

Robin, in the post you said:
“Rick had a larger point as well. The disk guys have an incredible story to tell and they aren’t telling it. I’ll be getting into some of that later this week.”

Could you shed some light on that interesting disk guys’ story? Thanks!

- amir

Jim Thompson Sunday, 28 October, 2007 at 1:52 am

You appear to be missing the contribution of SSDs to technologies like ZFS.

First, you need a workload where the ZIL has an impact.

The anticipaged improvement comes from separating the ZIL workload, which is small, sequential iops with a high desire for low latency, from more random workloads.
dedicated to the ZIL. Now think of how ZFS could use one or more SSDs to implement the ZIL, and specifically the types of access that work best with flash.

Now consider that hybrid drives (which you apparently hate) come with a ‘flash partition’ which ZFS could use to spread the ZIL out over several drives…

and connect the dots.

Leave a Comment

Previous post:

Next post: