The Intel Optane Memory (SSD) Preview: 32GB of Kaby Lake Cachingby Billy Tallis on April 24, 2017 12:00 PM EST
- Posted in
- PCIe SSD
- SSD Caching
- 3D XPoint
- Optane Memory
Last week, we took a look at Intel's first product based on their 3D XPoint non-volatile memory technology: the Optane SSD DC P4800X, a record-breaking flagship enterprise SSD. Today Intel launches the first consumer product under the Optane brand: the Intel Optane Memory, a far smaller device with a price that is 20 times cheaper. Despite having "Memory" in its name, this consumer Optane Memory product is not a NVDIMM nor is it in any other way a replacement for DRAM (those products will be coming to the enterprise market next year, even though the obvious name is now taken). Optane Memory also not a suitable replacement for mainstream flash-based SSDs, because Optane Memory is only available in 16GB and 32GB capacities. Instead, Optane Memory is Intel's latest attempt at an old idea that is great in theory but has struggled to catch on in practice: SSD caching.
Optane is Intel's brand name for products based on the 3D XPoint memory technology they co-developed with Micron. 3D XPoint is a new class of non-volatile memory that is not a variant of flash memory, the current mainstream technology for solid state drives. NAND flash memory—be it older planar NAND or newer 3D NAND flash—has fundamental limits to performance and write endurance, and many of the problems get worse as flash is shrunk to higher densities. 3D XPoint memory takes a radically different approach to non-volatile storage, and it makes different tradeoffs between density, performance, endurance and cost. Intel's initial announcement of 3D XPoint memory technology in 2015 came with general order of magnitude comparisons against existing memory technologies (DRAM and flash). Compared to NAND flash, 3D XPoint is supposed to be on the order of 1000x faster with 1000x higher write endurance. Compared to DRAM, 3D XPoint memory is supposed to be about 10x denser, which generally implies it'll be cheaper per GB by about the same amount. Those comparisons were about the raw memory itself and not about the performance of an entire SSD, and they were also projections based on memory that was still more than a year from hitting the market.
3D XPoint memory is not intended or expected to be a complete replacement for flash memory or DRAM in the foreseeable future. It offers substantially lower latency than flash memory but at a much higher price per GB. It still has finite endurance that makes it unsuitable as a drop-in replacement for DRAM without some form of wear-leveling. The natural role for 3D XPoint technology seems to be as a new tier in the memory hierarchy, slotting in between the smaller but faster DRAM and the larger but slower NAND flash. The Optane products released this month are using the first-generation 3D XPoint memory, along with first-generation controllers. Future generations should be able to offer substantial improvements to performance, endurance and capacity, but it's too soon to tell how those characteristics will scale.
The Intel Optane Memory is a M.2 NVMe SSD using 3D XPoint memory instead of NAND flash memory. 3D XPoint allows the Optane Memory to deliver far higher throughput than any flash SSD of equivalent capacity, and lower read latency than a NAND flash SSD of any capacity. The Optane Memory is intended both for OEMs to integrate into new systems and as an aftermarket upgrade for "Optane Memory ready" systems: those that meet the system requirements for Intel's new Optane caching software and have motherboard firmware support for booting from a cached volume. However, the Optane Memory can also be treated as a small and fast NVMe SSD, because all of the work to enable its caching role is performed in software or by the PCH on the motherboard. 32GB is even (barely) enough to be used as a Windows boot drive, though doing so would not be useful for most consumers.
Intel Optane Memory uses a PCIe 3.0 x2 link, while most M.2 PCIe SSDs use the full 4 lanes the connector is capable of. The two-lane link allows the Optane Memory to use the same B and M connector key positions that are used by M.2 SATA SSDs, so there's no immediate visual giveaway that Optane Memory requires PCIe connectivity from the M.2 socket. The Optane Memory is a standard 22x80mm single-sided card but the components don't come close to using the full length. The controller chip is far smaller than a typical NVMe SSD controller, and the Optane Memory includes just one or two single-die packages of 3D XPoint memory. The Optane Memory module has labels on the front and back that contain a copper foil heatspreader layer, positioned to cool the memory rather than the controller. There is no DRAM visible on the drive.
|Intel Optane Memory Specifications|
|Capacity||16 GB||32 GB|
|Form Factor||M.2 2280 B+M key|
|Interface||PCIe 3.0 x2|
|Memory||128Gb 20nm Intel 3D XPoint|
|Sequential Read||900 MB/s||1350 MB/s|
|Sequential Write||145 MB/s||290 MB/s|
|Random Read||190k IOPS||240k IOPS|
|Random Write||35k IOPS||65k IOPS|
|Read Latency||7µs||9 µs|
|Write Latency||18µs||30 µs|
|Active Power||3.5 W||3.5 W|
|Idle Power||1 W||1 W|
|Endurance||182.5 TB||182.5 TB|
The performance specifications of Intel Optane Memory have been revised slightly since the announcement last month, with Intel now providing separate performance specs for the two capacities. Given the PCIe x2 link it's no surprise to see that sequential read speeds are substantially lower than we see from other NVMe SSDs, with 900 MB/s for the 16GB model and 1350 MB/s for the 32GB model. Sequential writes of 145 MB/s and 290 MB/s are far slower than consumer SSDs are usually willing to advertise, but are typical of the actual sustained sequential write speed of a good TLC NAND SSD. Random read throughput of 190k and 240k IOPS is in the ballpark for other NVMe SSDs. Random write throughput of 35k and 65k IOPS are also below the peak speeds advertised my most consumer SSDs, but on par with mainstream TLC and MLC SSDs respectively for actual performance at low queue depths.
Really it's the latency specifications where Optane Memory shines: the read latency of 7µs and 9µs for the 16GB and 32GB respectively are slightly better than even the enterprise Optane SSD DC P4800x, while write latency of 18µs and 30µs are just 2-3 times slower. The read latencies are completely untouchable for flash-based SSDs, but the write latencies can be matched by other NVMe controllers, but only because they cache write operations instead of performing them immediately.
The power consumption and endurance specifications don't look as impressive. 3.5W active power is lower than many M.2 PCIe SSDs and low enough that thermal throttling is unlikely to be a problem. The 1W idle power is unappealing, if not a bit problematic. Many M.2 NVMe SSDs will idle at 1W or more if the system is not using PCIe Active State Power Management and NVMe Power States. The Optane Memory doesn't even support the latter and will apparently draw the full 1W even in a well-tuned laptop. Since these power consumption numbers are typically going to be in addition to the power consumption of a mechanical hard drive, an Optane caching configuration is not going to offer decent power efficiency.
Meanwhile write endurance is rated at the same 100GB/day or 182.5 TB total for both capacities. Even though a stress test could burn through all of that in a week or two, 100GB/day is usually plenty for ordinary consumer use. However, a cache drive will likely experience a higher than normal write load as data and applications will tend to get evicted from the cache only to be pulled back in the next time they are loaded. More importantly, Intel promised that 3D XPoint would have on the order of 1000x the endurance of NAND flash, which should put these drives beyond the write endurance of any other consumer SSDs even after accounting for their small capacity.
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Billy Tallis - Wednesday, April 26, 2017 - linkAs long as you have Intel RST RAID disabled for NVMe drives, it'll be accessible as a standard NVMe device and available for use with non-Intel caching software.
fanofanand - Tuesday, April 25, 2017 - linkI came here to read ddriver's "hypetane" rants, and I was not disappointed!
TallestJon96 - Tuesday, April 25, 2017 - linkToo bad about the drive breaking.
As an enthusiast who is gaming 90% of the time with my pc, I don't think this is for me right now. I actually just bought a 960 evo 500gb to compliment my 1 tb 840 evo. Overkill for sure, but I'm happy with it, even if the difference is sometimes subtle.
This technology really excites me. If they can get a system running eith no Dram or Nand, and just use a large block of Xpoint, that could make for a really interesting system. Put 128 gb of this stuff paired with a 2c/4t mobile chip in a laptop, and you could get a really lean system that is fast for every day usage cases (web browsing, video watching, etc).
For my use case, I'd love to have a reason to buy it (no more loading times ever would be very futuristic) but it'll take time to really take off.
MrSpadge - Tuesday, April 25, 2017 - link> no more loading times
Not going to happen, because there's quite some CPU work involved with loading things.
SanX - Tuesday, April 25, 2017 - linkBlahblahblah indurance, price, consumption, superspeed. Where they are? ROTFLOL At least don't show these shameful speeds if you opened your mouth this loud, Intel. No one will ever look at anything less then 3.5GB/s set by Samsung 960 Pro if you trolled about superspeeds.
cheshirster - Wednesday, April 26, 2017 - linkIs there any technical reasoning why this won't work with older CPU's?
I don't see this being any different than Intel RST.
KAlmquist - Thursday, April 27, 2017 - linkI think that Intel SRT caches reads, whereas the Optane Memory caches both reads and writes. My guess is that when Intel SRT places data in the cache, it doesn't immediately update the non-volatile lookup tables indicating where that data is stored. Instead, it probably waits until a bunch of data has been added, and then records the locations of all of the cached data. The reason for this would be that NAND can only be written in page units. If Intel were to update the non-volatile mapping table every time it added a page of data to the cache, that would double the amount of data written to the caching SSD.
If I'm correct, then with Intel SRT, a power loss can cause some of the data in the SSD cache to be lost. The data itself would still be there, but it won't appear in the lookup table, making it inaccessible. That doesn't matter because SRT only caches reads, so the data lost from the cache will still be on the hard drive.
In contrast, Optane Memory memory presumably updates the mapping table for cached data immediately, taking advantage of the fact that it uses a memory technology that allows small writes. So if you perform a bunch of 4K random writes, the data is written to the Optane storage only, resulting in much higher write performance than you would get with Intel SRT.
In short, I would guess that Optane Memory uses a different caching algorithm than Intel SRT; an algorithm that is only implemented in Intel's latest chipsets.
That's unfortunate, because if Optane Memory were supported using software drivers only (without any chipset support), it would be a very attractive upgrade to older computer systems. At $44 or $77, an Optane Memory device is a lot less expensive than upgrading to an SSD. Instead, Optane Memory is targeted at new systems, where the economics are less compelling.
mkozakewich - Thursday, April 27, 2017 - linkI would really like to see the 16GB Optane filled with system paging file (on a device with 2 or 4 GB of RAM) and then do some general system experience tests. This seems like the perfect solution: The system is pretty good about offloading stuff that's not needed, and pulling needed files into working memory for full speed; and the memory can be offloaded to or loaded from the Optane cache quickly enough that it shouldn't cause many slowdowns when switching between tasks. This seems like the best strategy, in a world where we're still seeing 'pro' devices with 4 GB of RAM.
Ugur - Monday, May 1, 2017 - linkI wish Intel would release Optane sticks/drives of 1-4TB sizes asap and sell them for 100-300 more than SSDS of same size immediately.
I'm kinda disappointed they do this type of tiered rollout where it looks like it'll take ages until i can get an Optane drive at larger sizes for halfway reasonable prices.
Please Intel, make it available asap, i want to buy it.
abufrejoval - Monday, May 8, 2017 - linkWell the most important thing is that Optane is now real a product on the market, for consumers and enterprise customers. So some Intel senior managers don’t need to get fired or cross off items on their bonus score cards.
Marketing will convince the world that Optane is better, most importantly that only Intel can have it inside: No ARM, no Power no Zen based server shall ever have it.
For the DRAM-replacement variant, that exclusivity had a reason: Without proper firmware support, that won’t work and without special cache flushing instructions it would be too slow or still volatile.
Of course, all of that could be shared with the competition, but who want to give up a practical monopoly, which no competition can contest in court before their money runs out.
For the PCIe variant Intel, chipset and OS dependencies are all artificial, but doesn’t that make things better for everyone? Now people can give up ECC support in cheap Pentiums and instead gain Optane support for a premium on CPUs and chipsets, which use the very same hardware underneath for production cost efficiency. Whoever can sell that, truly deserves their bonus!
Actually, I’d propose they be paid in snake oil.
For the consumer with a linear link between Optane and its downstream storage tier, it means the storage path has twice as many opportunities to fail. For the service technician it means he has four times as many test scenarios to perform. Just think on how that will double again, once Optane does in fact also come to the DIMM socket! Moore’s law is not finished after all! Yeah!
Perhaps Microsoft could be talked into creating a special Optane Edition which offers much better granularity for forensic data storage, and surely there would be plenty of work for security researchers, who just love to find bugs really, really deep down in critical Intel Firmware, which is designed for the lowest Total Cost of TakeOwnership in the industry!
Where others see crisis, Intel creates opportunities!