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Fusion-io builds SSD bridge between SLC, MLC

Fusion-io has taken a step towards bridging the gap between expensive single-level cell (SLC) and cheaper but slower and less reliable multi-level cell (MLC) NAND Flash.

The startup calls the new solid state drive (SSD) technology single mode level cell (SMLC) and expects to be shipping products in its ioDrive and ioDrive Duo PCI Express product lines this quarter.

Fusion-io says SMLC “combines a cost-effective MLC-based solid-state solution with the endurance and performance of SLC,” but it’s really a third option that falls between SLC and MLC in price and performance.

Fusion-io hasn’t released performance numbers, but CTO David Flynn says the SMLC drives close the gap in write speeds and endurance cycles between MLC and SLC. SMLC drives store two bits per cell and come in capacities of 160 GB and 320 GB just like MLC drives – although the SMLC drives require greater overprovisioning to reach those capacities. Generally, SLC drives write about 20% to 30% faster than MLC drives and have about 10 times the write cycles. For the most part, MLC’s shortcomings have kept it out of enterprise SSD products while SLC’s price still scares off a lot of people.

“(SMLC) is very close to SLC,” Flynn said. “I wouldn’t say it’s exactly SLC, but it’s sufficiently close for most uses cases.”

Flynn says SMLC drives will roughly split the difference in cost between its performance SLC ($30 per GB) and capacity MLC ($15 per GB) drives.

Fusion-io already ships enterprise MLC drives that Hewlett-Packard sells as the HP StorageWorks 320GB IO Accelerator.

“This (SMLC) is subtly different,” Flynn says. “Now we can get endurance and performance characteristics of SLC.”

The difference is in the way the controller manages the NAND Flash, he says. “We don’t need special MLC Flash, that would defeat the purpose,” Flynn said. “The purpose is not to have special requirements.”

Dell also sells Fusion-io cards, and IBM has released test results and is committed to selling Fusion-io SSDs down the road.

None of Fusion-io’s partners have publicly signed on to the SMLC cards yet, but Enterprise Strategy Group analyst Mark Peters says SMLC will likely become a third category for NAND Flash alongside SLC and MLC, at least until NAND is replaced by better technology.

“More people will follow, because they have to,” Peters says. “It’s logical. Every piece of research we’ve done says the No. 1 reason people aren’t adopting solid state is price, and this is a move to get the price down.”

Flynn agrees that Fusion-io won’t be the only vendor with SMLC, even if others call it something different.

“We’re first, but we don’t think we’ll be the last,” he said. “It’s too compelling.”

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