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How Long Does NAND Flash Memory Last?: Page 3 of 4

Mills maintains that the write idiosyncrasies of NAND are no different from the inherent limitations of other technologies. "If you take a hard drive with a life expectancy of three to five years, it's the mechanics of the drive that usually fail in the form of a head crash where the head gets so close to the media that it touches it and destroys the data," he says. "These kinds of failures happen unpredictably, whereas with NAND SSDs, their composition is entirely electrical and semiconductor. They present a different kind of failure mechanism where breakdowns begin to appear after you do so many writes and begin to see increases in failures of blocks of NAND, which allows you to take action before total failure."

One of the most active areas of NAND research is in multi-level cell NAND, which offers far greater density than its SLC counterpart, which is used today in enterprise computing. MLC offers even greater opportunity to enterprises than SLC, but its use is hindered by very low write capability. "In essence, SLC is first generation NAND flash with one bit per cell," says Mills. "With MLC, you have densities of two, three or more bits per cell. The problem with reliability is that as you go to the higher density, the number of writes per bit that you can do shrinks. What we are working on now is to figure out a way that we can utilize MLC and get enterprise reliability, at the same time that we drive the costs down."

It is higher performance and lower cost in configuration (where large numbers of hard drives can be replaced with fewer SSDs) that is pushing NAND Flash and SSDs. NAND SSD manufacturers have the immediate goals of making their systems equivalent to hard drives in endurance, which is where the write wear-leveling algorithms come in. These algorithms have given NAND Flash and SSD the three-to five year life cycle endurance, and have essentially rendered an initial write limitation (at least for SLCs) a non-issue. But the quest to overcome MLC write limits continues.

"As each of these technologies come into play, each finds its price/performance point and the role that it plays," says Adams. "We are likely to see these technologies incorporated into enterprise life cycle management that features tiers of storage with performance characteristics that are most amenable to SSDs or to hard drives."

Many major tech vendors are devoting a lot of resources to developing better and less expensive NAND technology as they expect the market to continue growing. Major players include Micron, Intel Corp. (Nasdaq: INTC), Samsung Corp. , ST Electronics, SanDisk Corp. (Nasdaq: SNDK), and Toshiba Corp. (Tokyo: 6502) Research firm Gartner Inc. originally predicted the overall NAND market would grow 30 percent this year, but it has cut that forecast in half because of a softening market and an oversupply of product. Analysts estimate the overall consumer and business market for NAND at around $50 billion to $60 billion annually and say that it will stay at that level through 2012 as declining prices offset growing demand.