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Optane Memory – A bridge between DRAM and storage

intel.com

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Re: Optane Memory – A bridge between DRAM and storage

#81

Post by usrusr »

nilanjonB wrote: post #43
2bluesc wrote: post #16

Anandtech, as usual, has a good article: http://www.anandtech.com/show/11227/intel-launches-optane-me... > The Optane Memory products are squeezing into a relatively small niche for limited budgets that require a lot of storage and want the benefit of solid state performance without paying the full price of a boot SSD. Intel notes that Optane Memory caching can be used in front of hybrid drives and SATA SSDs, but the…

I'm wondering what market their actually aiming for? non-NVMe drive users? If the gains aren't that significant, why would people buy it and why would PC maker want to use it?

One presentation was comparing an 8GB+HDD system to a 4GB+Optane+HDD system, showing off how the low RAM hybrid was much faster at selected tasks (carefully selected tasks, I presume). This is probably the market, another indication is the surprisingly low price.

The price difference between 4 GB and 8 GB of RAM cannot be enough to compensate for the Optane module, but if the Optane combination uses less battery than the bigger RAM and if enough benchmarks and/or magazine performance comparison use cases coincide with tasks where the hybrid shines, then some low end manufacturers might successfully sell the RAM downgrade as an upgrade option.

Re: Optane Memory – A bridge between DRAM and storage

#82

Post by hl5 »

freeone3000 wrote: post #5

It looks to be an accelerator cache for HDDs, but slower than an SSD, with fairly low capacity. And it requires a 7th gen intel processor, so this isn't a performance boost for older PCs either. Exactly who is this aimed at?

I think it could extend battery time for large format tablets and car computers.

Re: Optane Memory – A bridge between DRAM and storage

#83

Post by patrickg_zill »

2GBytes/second as RAM is as good as DDR1 memory.

So take a CPU with more memory channels on it, run at least 1 Optane per channel, run hundreds of VMs on it, everything runs from this slower RAM, but it is in memory and you only touch the SSDs for updating the disk. Once the cache is warmed up performance should be just fine.

Re: Optane Memory – A bridge between DRAM and storage

#84

Post by wtallis »

usrusr wrote: post #81
nilanjonB wrote: post #43

Earlier quoted context omitted.

I'm wondering what market their actually aiming for? non-NVMe drive users? If the gains aren't that significant, why would people buy it and why would PC maker want to use it?

One presentation was comparing an 8GB+HDD system to a 4GB+Optane+HDD system, showing off how the low RAM hybrid was much faster at selected tasks (carefully selected tasks, I presume). This is probably the market, another indication is the surprisingly low price. The price difference between 4 GB and 8 GB of RAM cannot be enough to compensate for the Optane module, but if the Optane combination uses less battery than…

> "but if the Optane combination uses less battery than the bigger RAM"

With idle power specified as 0.9-1.2 W, I'm not expecting the Optane-based solutions to come out ahead on any battery life tests. PCIe power management is a horrific mess.

Re: Optane Memory – A bridge between DRAM and storage

#85

Post by wtallis »

mtgx wrote: post #68
ChuckMcM wrote: post #53

The 'win' in theory for this stuff is that it is much faster than SSDs at low queue depths and it is significantly more write tolerant. An interesting interesting system design might be a 2GB main memory with a 32GB swap partition on this device. That would be interesting because in idle mode it uses less power than an equivalent amount of DDR memory. So you could potentially build a laptop with good performance on l…

> Intel's claim has been in the past that its density can exceed SSDs by a healthy margin Seems doubtful they would reach that goal until SSDs hit some kind of hard plateau (kind of like HDDs did). Toshiba plans to make a 100TB SSD over the next couple of years, and I believe Samsung has already announced a 16TB SSD. I doubt 3D Xpoint can catch-up with those in the given time frame.

NAND flash memory already hit the wall for horizontal shrinks, and some products plowed past that limit and into the regime where day to day use was invoking the second level error correction methods to compensate for data degradation.

3D NAND turned the clock back on horizontal scaling and cell sizes by several years, and now the only scaling opportunity is to increase layer count. That's not going so well. Samsung started with 24 layers but didn't ship retail products until they hit 32 layers. Their 48 layers was about a year late and caused several products to be scrapped entirely. Toshiba's on their third generation 3D NAND and it's only just starting to show up in the market. SK Hynix is doing worse than Toshiba. Intel and Micron started off reasonably well with their 32-layer and are working on ramping up 64-layer.

By the end of this year, all four manufacturers should be shipping 64-layer (72 for SK Hynix) 3D NAND in volume, or else it's time to admit that 3D NAND just doesn't scale up as well as we hoped it would.

There's some reason to believe 3D XPoint memory might be able to avoid the worst vertical scaling problems that are holding back 3D NAND flash. Each pair of 3D XPoint layers can be pretty much isolated from the rest of the layers except at the edges, whereas 3D NAND is building columns of bits that run through all 64+ layers and have aspect ratios that are quite high.

Re: Optane Memory – A bridge between DRAM and storage

#86

Post by wtallis »

smlacy wrote: post #3

Quite a bit of marketing-speak here on the official site, without a lot of technical details. I know the Optane SSD drives are fast -- is this just device-side driver software that allows you to virtually expand available "RAM" and mmap it to the SSD? Why just i7 CPUs? Is there a hardware component? "Just download and install the driver..." (Linux?)

These consumer Optane Memory drives rely on a chipset hardware feature (that was introduced in the last generation) to work with Intel's caching strategy for Windows, which is complicated and ugly partly because it has to work around Windows limitations and partly because it has to enforce their product segmentation strategy. On Linux, it's just a NVMe device that can be used with any pre-existing caching software solution.

On the enterprise side, Intel is offering the Memory Drive Technology software that is a minimal hypervisor to present a pool of memory equal to about DRAM+85% of Optane, with the actual allocation managed by the hypervisor and opaque to the guest OS. The hypervisor can run on several generations of Xeon processors.

Re: Optane Memory – A bridge between DRAM and storage

#87

Post by wtallis »

misja111 wrote: post #7
smlacy wrote: post #3

Quite a bit of marketing-speak here on the official site, without a lot of technical details. I know the Optane SSD drives are fast -- is this just device-side driver software that allows you to virtually expand available "RAM" and mmap it to the SSD? Why just i7 CPUs? Is there a hardware component? "Just download and install the driver..." (Linux?)

What I understand of it, after skipping through all the marketing speak, is that the Optane Memory functions a cache for your SATA drive. The Optane cache is just a Optane SSD which uses some new and apparently faster 3D Nand technology. And about Linux; somewhere in the PDF with the technical details it states the requirement that your OS has to be 64 bit Windows ..

> "The Optane cache is just a Optane SSD which uses some new and apparently faster 3D Nand technology."

Optane products use 3D XPoint memory, which is not 3D NAND flash memory or any other kind of flash memory. It's probably a phase change memory, but Intel won't say so we have to wait for Chipworks to put it under an electron microscope.

The Optane Memory product for consumers is entirely centered around the use case of running Intel's SSD caching software for Windows, which requires a Skylake or newer chipset plus boot firmware that will only actually be available for Kaby Lake systems. The hardware feature they're relying on is a disgusting hack that Linux users want to stay far away from (and can, since there are generic caching solutions for Linux that work atop any block device).

Re: Optane Memory – A bridge between DRAM and storage

#88

Post by wtallis »

amluto wrote: post #57

I think you can (pending driver support?) plug one of these in and memory map it. On Linux, this means you'd see it as a "DAX" filesystem, and if you mmap(2) a file, you get a bona fide direct mapping of the hardware into your address space. This is very cool and would enable some interesting database-ish use cases. I'll believe it when I see the spec and the code.

No DAX yet. Both this consumer Optane Memory product and the enterprise Optane SSD announced last week are standard NVMe devices. For the enterprise market, Intel is providing mmap capability with a hypervisor-based software solution.

3D XPoint DIMMs are on the roadmap for next year.

Re: Optane Memory – A bridge between DRAM and storage

#89

Post by wtallis »

derefr wrote: post #73

I'd be interested in knowing what the performance of the caching is compared to e.g. using dm-cache with an SSD backing a HDD in Linux.

If you've got suggestions for how to meaningfully and realistically compare caching of a Windows boot volume against a Linux cache solution, please share. My usual suite of tests won't work well for this, and I'm open to suggestions for what to include in my new test suite.

Re: Optane Memory – A bridge between DRAM and storage

#90

Post by zeusk »

valarauca1 wrote: post #79
runeks wrote: post #70

Earlier quoted context omitted.

As far as I know, SSDs are closer to 0.1 ms latency (~10,000 random read IOPS at zero queue depth). That's still an improvement of more than an order of magnitude, though (0.009 ms according to the article).

100micro-seconds on writes. Reads are as low as 20micro-seconds [1] This is using an Samsung 860pro, so a generation behind the current generation. [1] https://www.cs.utah.edu/~manua/pubs/systor15.pdf

There was never a 860 pro, we had 850 pro (2.5" SATA) and then 950 and 960 pro which are m.2 only afaik (and nvme)
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