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NAND flash explained: MLC vs. SLC, part 1

In this segment of his presentation entitled “Making the case for solid-state storage” from Storage Decisions, Dennis Martin, president of Demartek, discusses the major differences in price, performance and storage capacities between MLC vs. SLC SSDs.

“If you’re going to do enterprise, ideally, you’ll want SLC if you can afford it. What we’re now finding is that the flash guys [who] make the flash controller at the low level are starting to put enterprise-grade stuff on reasonably good MLC, and they’ll come out with this enterprise MLC. So that’s why I say that mostly consumer for MLC-2; some of it actually is enterprise-grade. And that’s where all the marketing is, because you can get it a lot cheaper,” said Martin.

In his presentation, Martin recommends that administrators keep track -- even if it’s an estimate -- of the number of writes to their solid-state storage. Martin said that SLC typically has 10-20 times better endurance than MLC, and is twice as expensive, with a typical life span of 100,000 write cycles. MLC usually lasts about 10,000 write cycles, he said, but enterprise MLC should have about 30,000 write cycles.

“It turns out as you work on the physics, as you make the nanometers smaller -- the die in smaller nanometers -- you lose life cycles. So MLC -- two- and three- and four-bit -- they have 3,000 writes, or 1,000 writes per bit. So you don’t want to use those for your database or email applications,” said Martin.


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