Micron Flash Advance: Live Longer and Rewrite

Micron Technology (NYSE: MU) this week announced advancements in NAND flash memory durability that will allow for much longer life spans of flash drives.

Flash-based drives, called solid state drives (SSDs), have emerged as potential replacements for the traditionally platter-based storage medium. They run a lot cooler since there is no spinning media, and draw less power.

But on the down side, NAND flash is made of “cells,” with each cell holding data of only one bit (in a design called single-level cell, or SLC) or two bits (a multi-level cell, or MLC). That may ultimately become less of a shortcoming, since Intel and Micron announced plans for three bits per cell in August.

But a larger hurdle has been the fact that every time data is written to a bit, the cell erodes just a tiny amount. Over time, with repeated writes, the cells eventually become unusable. (As the thinking goes, MLC drives suffer wear even faster, due to their cells having twice as many points to write to.)

So while SSD was very appealing as a replacement for high-speed hard drives, questions remained about just how long the flash drives would last.

Now, Micron’s breakthrough raises the lifespan of both SLC and MLC drives. It has created a new 34-nanometer NAND memory manufacturing process that can double flash-based enterprise storage capacity and increase their write cycles.

Micron’s new MLC Enterprise NAND device can handle up to 30,000 write cycles, a six-fold increase in endurance when compared to standard MLC NAND. Its 34nm SLC Enterprise NAND device can handle up to 300,000 write cycles, a three-fold increase in endurance when compared to standard SLC NAND.

“By leveraging our mature 34nm NAND process, Micron has developed Enterprise NAND products that support customers’ high-endurance requirements,” Brian Shirley, vice president of Micron’s memory group, said in a statement. “These products ensure that enterprise organizations have a highly reliable NAND flash solution — be it MLC or SLC — for design into the broader enterprise storage platform.”

Micron’s new Enterprise products also support the Open NAND Flash Interface (ONFI) 2.1 synchronous interface, which increases the data transfer rates by four or five times over previous interfaces.

It’s a significant milestone for the industry, one one that’s likely to increase confidence in the technology, according to Bob Merritt, principal analyst with Convergent Semiconductors.

That’s because NAND flash-based storage is more or less new territory for everyone involved, from semiconductor makers to OEMs to end users — who are all still feeling out the limits of the technology, he said.

Most users are not terribly concerned with mean time before failure (MTBF) because things like memory and hard drives tend to last for years and many uses, he told InternetNews.com. On the other hand, SSD’s limitations are making people more aware of shorter technology lifespans.

“Now we have to match reality of the technology with a true understanding of what the limits of the technology are,” he said. “NAND SSD technologies started with consumer applications, and as we get more experienced with what acceptable performance is, NAND progresses closer and closer to those enterprise applications.”

“Micron’s effort to extend the reliability is another step toward understanding where these limits are and extending the range where NAND can operate without concerns of exceeding that durability limit,” Merritt said.

Micron provides the flash to OEMs to make their own capacities in addition to making its own SSD drives as well. Its SLC chips are 16Gbits in capacity and its MLC chips are 32Gbit. The configuration and capacity is left to OEMs.

Micron said that it’s offering samples of its Enterprise NAND products to customers and controller manufacturers, and that it expects the technology to be in volume production in early 2010.

(Update corrects information about Micron’s SSD offerings.)

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