Where’s The Bottleneck?
TH: You mentioned striping SSDs. What performance increase have you seen there? Does it scale linearly or taper off like hard drives?
LK: Oh, yeah. It gets up to about 600 or 700 MB/sec when we've messed around with an integrated Intel RAID controller. After that, adding any more doesn't really help. So technically, I guess, after the third drive. You can gain capacity after that, just not performance. But it does scale especially if you go with a discrete RAID controller. You can benchmark with Iometer and see the scores pretty much double with two drives. The bandwidth doubles. The random IOPS will pretty much double. At IDF last year, we had four of the E-class Kingston drives, and we were displaying 1,000 MB/sec sequential read speeds using a high-end Adaptec RAID controller.
TH: Are we being bottlenecked already by the SATA 3 Gb/s interface? Do we need to move SSDs onto a 6 Gb/s connection?
LK: I think you're going to need the controllers to support it. That's probably a bigger issue. Some drives already have the current SATA II spec pinned in terms of performance. Tony, how much better will SATA III make SSDS?
TC: For the next generation, SATA III, we still need to go back and look at the semiconductor road map. How fast of a raw speed can we get from the NAND flash? Also, the design architecture from the SATA SSD controller interface—how many channels can be accessed at the same time? Those will determine the upgrades necessary for SATA III in the future. Everybody is concerned about how we can accommodate 6 Gb/s transfer rates and how to accomplish that. I know Micron has already announced the first one. Everybody is looking to see how this will perform in the next two years.
TH: So I shouldn't get excited about product shipping next week.
LK: Yeah, I don't think Intel is talking about it on desktop boards until 2011. But it's a big deal. It means adoption from the big PC OEMs. At this point, it's more of a DIY play.There are several motherboards already supporting 6 Gb/s via add-on controllers. It's exciting, to be sure, but I think from a consumer standpoint USB 3.0 is a lot more exciting to me right now. On the USB side—I know this is a little off-topic—we're shipping 128GB and 256GB USB drives. A guy who's buying that isn't just going to copy a couple of files over. Try moving 40GB at USB 2.0 speeds. You can go get lunch, come back, and it's still going, right?
TH: Oh, sure! I put your drive in a $25 enclosure and—bam! All that speed ran into the USB interface brick wall. Going to USB 3.0 suddenly gets us a lot more speed for our external storage.
LK: Absolutely. And at that point, could it be bootable? Could you boot to an external SSD on USB 3.0? At 4.8 Gb/s? Yeah, you probably could.
TH: Great idea. So that's your next product?
LK: [laughs] Yeah, we'll see.