Does 3D XPoint Spell the End for Flash Storage?


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If your storage systems are due a refresh and you are planning future purchases, then there's a huge elephant in the room that needs addressing: Intel and Micron's high performance 3D XPoint technology.

Touted by Intel and Micron as the first new memory tier to be launched since the introduction of NAND flash memory in 1989, its launch could have a significant effect on the storage market and your purchasing decisions.

So here's the problem: There's a good chance you've been looking at flash SSD-based systems to replace some of your conventional storage capacity, but not much is known about 3D XPoint yet—even though it should start appearing in significant quantities in the next 18-24 months.

Do you really want to be buying an expensive flash SSD system offering higher performance than an HDD-based array just as a new tier of even higher performance storage hits the market?

Before answering that question, let's do a quick recap about what we know about 3D XPoint. Intel and Micron have been fairly coy about the precise nature of the technology that underlies it, but we do know that it is non-volatile — so it's more like NAND flash (or even HDD storage) than volatile DRAM.

But according to Intel, 3D XPoint is up to 1,000 times faster than flash, with 1,000 times more endurance (or tolerance to write cycles.) It's also up to ten times denser than DRAM, which is important as that means there's the potential for manufacturing costs to be low. And its latency is about ten times lower than an enterprise class SSD connected over NVM Express (NVMe.)

It's still slower than DRAM, but it will also be less expensive.

This means that in the storage hierarchy, 3D XPoint slots in between DRAM and NAND: cheaper but slower than volatile system memory, but much faster though more expensive than non-volatile SSDs or system-mounted flash cache modules.

By its nature 3D XPoint is more like fast but expensive flash than slow but cheaper DRAM, because it's a non-volatile storage medium. And Intel promises that SSDs filled with 3D XPoint storage rather than conventional NAND will offer up to ten times the performance.

But due to its durability and its high density (compared to DRAM,) Intel says it can also serve as a single combined pool of high-speed system and storage memory.

So the question is really this: how will 3D XPoint be used: in system memory as a replacement for volatile DRAM, or as a high-speed replacement for NAND in conventional solid state storage systems and flash caches?

Jim Handy, solid state storage expert and semiconductor analyst at Objective Analysis, believes that it's the former use case that will be the most popular. "The point is to achieve better performance for less cost, and that is (best) done by reducing DRAM use through the addition of 3D XPoint," he says.

"Any use of 3D XPoint to reduce SSD or HDD use would be to replace a cheaper technology with a more costly one with little, if any, speed gain," he adds, "I do not expect for 3D XPoint to impact SSD sales at all."

That may sound counterintuitive, but if you have a fixed budget, then spending $100 on 3D XPoint instead of DRAM will often lead to a performance boost.

That's because even though 3D XPoint is a little slower than DRAM you can buy more 3D XPoint than DRAM for your money, thus capturing more data or instructions that would otherwise require a much slower SSD or HDD access, Handy explains. "So adding 3D XPoint instead of DRAM will make your system faster," he says.

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