The Solid Future Of Solid-State Disks

The replacement for platter-based disk drives may be as close as your pocket MP3 player. SSD, or solid-state disk, systems are changing the way enterprises views storage for workstations and data centers. They're less expensive to run and cool and are more dependable.

Lined up right now to satisfy the not-yet-overwhelming demand for SSD devices are Adtron Corp., Altec ComputerSysteme //cq//, Curtis, Samsung, SanDisk, STEC Corp. and Super Talent Technology. Seagate and Western Digital currently offer hybrid drives but have yet to commit to an all-SSD lineup. Microsoft is partnering with Seagate and others to push hybrid drives for "instant-on" fastboot capabilities in Windows Vista.

Although prices have yet to hit the critical mass needed to spark a market revolution, SSDs are peeking over the horizon. Near-instantaneous access times for critical databases, instant-on states for workstations and MTBFs measured in decades mean that when solid-state disks break through the price barrier, platter-based drives will become relics.

Storage vendors have dragged some hefty baggage into the 21st century. The basic IDE interface, for example, is more than 20 years old; SCSI traces its roots back to Shugart Associates' SASI interface, introduced in 1979. Perhaps most onerous is the medium itself: A rotating magnetized disk that can cause major headaches under the best data center conditions. Failure of a single drive—or more catastrophically, an entire array—and it's twilight time for your data.

Fortunately, that's changing.

SSDs, or solid-state drives, sometimes referred to as flash drives, use no moving parts. They consist of large quantities of RAM attached to an appropriate interface. Once packaged, the drives are no different from their spinning platter-based brethren as far as interface controllers on host systems or, for example, large NAS arrays, are concerned. The key difference is the lack of moving parts. Instead of a motor and series of heads, controllers manage data flow from each bank of RAM, passing information to the attached drive controller, which in turn passes it to the host system. Data access is near instantaneous.

Not only do transfer speeds outstrip platter-based disk systems, the power needs of SSDs are considerably lower. For example, Samsung's 32-GB notebook, with its 2.5-inch SSD, consumes 95 percent less power than comparable disk-based drives, with three times the average disk-access speed on a lowly UATA-33 bus. Another advantage SSDs have over their magnetic kin is noise reduction—we've worked with new SATA-3 platter-based drives that sound like boxes of rocks.

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So what's the downside? Currently, the per-gigabyte cost of SSD storage for, as an example, a 2.5-inch notebook drive is $10.95, based on a 2.5-inch SATA SSD offering from SanDisk. That sounds expensive. Yet, compare that to just a year ago, when a 32-GB 2.5-inch SATA SSD from Advanced Media cost a whopping $31.25 per gigabyte. This rapid drop in price means that SSDs may become a more viable alternative for end users and data centers alike. Still, the price for rotating media continues to fall as well. In 2006, the price-per-gigabyte of a platter-based drive of a similar interface to the Advanced Media SSD was roughly $0.30 per gigabyte. Clearly, SSD has quite a ways to go before it's practical to dump magnetic media altogether.

A station on the road toward SSDs is the hybrid drive. These devices bridge the gap between platter drives and SSDs by using not only rotating media but also a bank of RAM (128 MB to 512 MB, in most cases) to cache frequently accessed data. This caching means that systems using these hybrid drives can enjoy the same "instant-on" capabilities (or in the case of enterprise, instant data access) of SSD-based systems without the price overhead. At about $1.02 per gigabyte, hybrid drives come in at attractive price, comparatively, and offer some of the advantages of SSDs.

Then there's the millions of dollars spent every year on data center heat management. Platter-based drive motors produce significant heat that must be dissipated. While SSDs do get warm, they run much cooler than platter-based drives.The Magic Touch

As noted, the robustness of SSDs compared with disk systems is a huge draw. Currently, NASA employs SSDs in quite literally mission-critical applications. For example, flight data recorders on the space shuttle fleet are largely turned over to SSDs. While the best disk drive can absorb G loads in the high double digits, SanDisk offers a 320-GB Ultra320 Wide-SCSI SSD drive that can withstand 1,500 Gs of impact for .5 millisecond. The most violent takeoff and landing impacts rarely exceed 9 Gs. Clearly, the advantage goes to SSDs once again.

NASA isn't the only government agency using SSDs. The Land Warrior system currently undergoing development for the Army and Marines, and its eventual replacement, Future Warrior, will incorporate an ARM X-Scale-based computer in the computer subsystem used for targeting, GPS navigation, command/control/communications and information—and all of these items will be tied into an SSD for storage of critical data. These two systems are designed to give commanders total battlefield integration capabilities, from real-time man-to-man targeting data all the way to health status and precise location of individual soldiers, both of which will hopefully give individual soldiers equipped with Land Warrior or Future Warrior a clearer picture of the disposition of their comrades, the battlefield and opponents as events unfold around them.

It Isn't Right

Still, no matter how attractive, quiet, low-power, low-heat, and ultra-durable SSDs may be, if the price isn't right, they won't find their way into most workstation and server applications. The issue of price doesn't appear to be wholly the result of lagging technology, either. As we were preparing this article, we discovered that both the U.S. and Canadian Departments of Justice have leveled their guns at the big NAND/SSD manufacturers: Samsung and SanDisk are both facing investigations for violation of antitrust laws. The litigation may spread to other manufacturers of RAM storage devices, including Hitachi, Lexar, Micron and Toshiba. While it is impossible to tell what overall effect this may have on the price of diskless storage, and SSDs in particular, the fallout could benefit not only corporate users but end users, if the companies swept up in the litigation are driven to allow greater access to the technologies behind SSD. This investigation is focusing on anticompetitive price-fixing and collusion between manufacturers.SSDs will eventually replace the platter drive in all aspects. The bottleneck isn't technology, merely price. Soon, data centers will be quieter, cooler, more robust and, above all, faster.

TIMELINE

1985: Santa Clara Systems begins shipping SSD devices in the form of BatRam: battery backed-up storage devices for desktop systems

1988: SanDisk is founded by Dr. Eli Harari and begins to work toward solid-state storage solutions

1995: MSystem introduces flash RAM-based SSDs

2000: Card Flash to IDE adapters become widely available, allowing CF RAM cards to be used as substitute IDE devices

2006: SanDisk buys MSystem

Bill Silvey is an IT professional specializing in desktop-to-server workstation connectivity and enterprise solutions. He has worked for NASA, Advanced System Technologies and STAR Systems and is a freelance columnist for InformationWeek. Write to him at [email protected].