You know that a technology is climbing the hype curve when it appears on the bill for an MIT/Stanford VLAB (Venture Laboratory) evening meeting. That’s exactly what happened for Solid-State Drives (SSDs) on November 17 when SSDs were the technology of the evening. The event was a panel titled “SSDs: Game-Changing Technology for Better, Bigger, Faster Apps and App Dev.” The panel moderator was well-known storage analyst Tom Coughlin. Panelists included Fusion-io’s President and CTO David Flynn; Bill Watkins, Former CEO, Seagate; Mike Chenery, President, Pliant Technology; Mike Speiser, Managing Director, Sutter Hill Ventures; and Sam Pullara, Chief Technologist, Yahoo! Inc.
SSDs are one of three ways to fill the memory/storage gap called the “Flash zone” as discussed in the previous AgigA Tech blog entry, which described Flynn’s initial panel presentation. Although not a major consumer of NAND Flash memory devices, yet, SSD use is growing quickly because of the speed advantages they deliver over what can be achieved with rotating mechanical storage (hard disk drives). Flynn’s talk described the ideal conditions under which I/O-attached storage (including products offered by Fusion-io) can deliver stellar storage performance as measured in IOPS. Flynn’s presentation prompted the first panel question from moderator Coughlin: “Are hard disk drives dead?”
Flynn answered first. Unsurprisingly, he said “No.” Tape hasn’t died either, said Flynn, and neither has DRAM. None of these technologies is in danger of disappearing overnight. HDDs (hard disk drives) currently enjoy a huge cost/capacity lead over any competing storage technology (excluding tape) and HDDs will only disappear when they lose that lead.
Speiser also weighed in. Tape’s huge cost/capacity lead over HDD storage is the only factor that keeps tapes alive for their ultimate use: “offline storage inside of (hollowed-out) mountains.” Tapes will outlast HDDs added Speiser. “They’re the cockroaches of the storage industry.” Chenery, who left HDD vendor Fujitsu in 2006 to start SSD supplier Pliant, also spoke favorably about HDDs. “No one wants a mechanical drive in their computer,” said Chenery, because of the power consumption and susceptibility to physical shock. However, “they provide so much value for capacity” he explained. “In 30 years, who knows?”
Watkins disagreed. “No one cares what’s in their PCs. Consumers think about the applications they want to run. Then they find the best hardware to fit their needs.” Watkins is more concerned by the applications that consumers will be using in five years. His conclusion: all mobility products will evolve into Flash-only use because Flash memory provides superior form factors for small, mobile end products. Meanwhile, cloud storage may obsolete large HDDs in laptops because it’s too dangerous to carry around all that valuable data in a form where it can be lost, stolen, damaged, or destroyed. Yahoo’s Pullara smiled at Watkins’ comment about cloud storage and quipped “How about unlimited storage (in Yahoo’s cloud)? Can you beat that, Google?”
“So if HDDs aren’t going away any time soon,” asked Coughlin, “why did you (Chenery) start Pliant?”
“Because no one would listen to me” replied Chenery, who feels that SSDs are clearly going to redefine they way computer systems are architected.
Speiser jumped on the bandwagon. “We’re looking to invest in companies that have fundamentally rethought applications to back out assumptions based on spinning media.”
Pullara concurred. “Look at anti-spam in 2003” he said. The need to maintain extensive lists of spam sources has soared since then. Maintaining those lists on slow HDDs would make it impossible to reject spam in real time, given the rising volume of spam emails.
Watkins returned the discussion to mobile applications. “The sweet spot for Flash is in the hand,” he said. SSDs must reach 100-Gbyte capacities for netbooks while enterprise applications require terabytes of data storage and corresponding changes in server architecture.
The question of data reliability and trust then arose. Flash memory has well-documented, well-understood wearout and failure mechanisms. In fact, Flash vendors have been far more open and informative about these technology issues than have HDD vendors. As a result, people better understand Flash failure modes and are more aware of them. Chenery grinned and asked “Why would you trust your data to a flying head on a disk?” referring to the incredibly small gap between the read/write head and the spinning media. Head crashes are a well-known HDD failure mechanism. “Flash memory has its idiosyncrasies, but technology overcomes a lot of these” said Chenery. “You manage these idiosyncrasies with appropriate controllers, software, and use models.” In the end said Chenery, system-level designers shouldn’t trust any of the HDD or SSD vendors. They should test and verify reliability claims.
In addition, said Chenery, SSDs don’t “fall off the cliff” (fail catastrophically like HDDs). They provide deterministic, predictable performance that allows for soft failures, usually seen as a gradual capacity decrease as control firmware walls off bad blocks in the Flash memory and moves data to good blocks. Most SSDs will decline in performance over time, claimed Chenery. They must be designed specifically to not decline in performance at the subsystem level. “Getting Flash to deliver deterministic performance in a random environment is hard. It requires enormous computing power.”