Is 3D XPoint in trouble?

by Robin Harris on Thursday, 6 October, 2016

The Register’s Chris Mellor and SemiAccurate’s Charlie Demerjian are throwing shade on Intel’s claims for 3D XPoint. While it’s great fun to tweak the giants of tech – as I often do – I think they are likely wrong in their interpretation of the data backing their arguments.

As Mr. Mellor wrote:

In contrast to the wildly optimistic Intel “1,000 times faster than NAND” claims when XPoint was launched, the Micron pitch presented a 10-times improvement over NAND in terms of IOPS and latency, and four times more memory footprint than DRAM per CPU.

Mr. Demerjian goes further in his comments:

Latency missed by 100x, yes one hundred times, on their claim of 1000x faster, 10x is now promised and backed up by tests. More troubling is endurance, probably the main selling point of this technology over NAND. Again the claim was a 1000x improvement, Intel delivered 1/333rd of that with 3x the endurance.

Chips vs systems
Intel and Micron are chip folks. I’m confident that at the chip/media level, the results that Intel reported are close – despite marketing rounding-up – but when talking about SSDs, Optane or QuantX, the subject is a system, not media. A system with a CPU, lots of software, buffers, caches, bandwidth and, finally, media.

Example
Back when RAID arrays were a radical new technology in the early 90s, the simple fact that you could gang together a half dozen disks and get a 5x performance improvement was a big deal. A little later caching came on the scene, and made RAID even more compelling.

But did adding in a layer of RAM – which was, let’s say, a million times faster – make RAID arrays a million faster? Of course not. The difference between write-back and write-through caching – and the associated engineering/test problems – played a major role as well.

Nor did replacing hard drives with SSDs make arrays as fast as raw NAND read numbers would suggest. Systems consist of cooperating parts, and making one part a thousand times faster doesn’t make all the other parts go faster too.

Mr. Mellor, of course, understands this, remarking:

We might say that the original XPoint claims referred to raw media comparisons and not system-level performance, a point not made clear in the original XPoint performance, density and endurance claims.

The StorageMojo take
Intel is not a marketing company. They are an engineering company selling to engineers and, as such, they often put a foot wrong when trying to reach the general tech public.

But that doesn’t explain why Intel/Micron rushed the 3D XPoint announcement: freeze out competitors; help Micron fight an acquisition; and/or panic at some perceived threat, such as Nantero? They might have consulted with their CPU colleagues on the problems that come from hyping, say, clock speeds, in the NetBurst days.

Whatever drove the announcement, they did themselves no favors by focusing on cell-level performance. But unlike those who read the announcement as a promise to deliver systems with those performance improvements, I’m pleased that they got into the market with 3D XPoint, because they are driving the industry faster than any startup could.

And that’s good for the industry and for computer systems buyers and users everywhere. The problems that I can see, such as schedule slips, appear normal for advanced technology.

Courteous comments welcome, of course.

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