Intel's Caching History

Intel's first attempt at using solid-state memory for caching in consumer systems was the Intel Turbo Memory, a mini-PCIe card with 1GB of flash to be used by the then-new Windows Vista features Ready Drive and Ready Boost. Promoted as part of the Intel Centrino platform, Turbo Memory was more or less a complete failure. The cache it provided was far too small and too slow—sequential writes in particular were much slower than a hard drive. Applications were seldom significantly faster, though in systems short on RAM, Turbo Memory made swapping less painfully slow. Battery life could sometimes be extended by allowing the hard drive to spend more time spun down in idle. Overall, most OEMs were not interested in adding more than $100 to a system for Turbo Memory.

Intel's next attempt at caching came as SSDs were moving into the mainstream consumer market. The Z68 chipset for Sandy Bridge processors added Smart Response Technology (SRT), a SSD caching mode for Intel's Rapid Storage Technology (RST) drivers. SRT could be used with any SATA SSD but cache sizes were limited to 64GB. Intel produced the SSD 311 and later SSD 313 with low capacity but relatively high performance SLC NAND flash as caching-optimized SSDs. These SSDs started at $100 and had to compete against MLC SSDs that offered multiple times the capacity for the same price—enough that the MLC SSDs were starting to become reasonable options for every general-purpose storage without any hard drive.

Smart Response Technology worked as advertised but was very unpopular with OEMs, and it didn't really catch on as an aftermarket upgrade among enthusiasts. The rapidly dropping prices and increasing capacities of SSDs made all-flash configurations more and more affordable, while SSD caching still required extra work to set up and small cache sizes meant heavy users would still frequently experience uncached application launches and file loads.

Intel's caching solution for Optane Memory is not simply a re-use of the existing Smart Response Technology caching feature of their Rapid Storage Technology drivers. It relies on the same NVMe remapping feature added to Skylake chipsets to support NVMe RAID, but the caching algorithms are tuned for Optane. The Optane Memory software can be downloaded and installed separately without including the rest of the RST features.

Optane Memory caching has quite a few restrictions: it is only supported with Kaby Lake processors and it requires a 200-series chipset or a HM175, QM175 or CM238 mobile chipset. Only Core i3, i5 and i7 processors are supported; Celeron and Pentium parts are excluded. Windows 10 64-bit is the only supported operating system. The Optane Memory module must be installed in a M.2 slot that connects to PCIe lanes provided by the chipset, and some motherboards will also have M.2 slots that do not support Optane Caching or RST RAID. The drive being cached must be SATA, not NVMe, and only the boot volume can be cached. Lastly, the motherboard firmware must have Optane Memory support to boot the cached volume. Motherboards that have the necessary firmware features will feature a UEFI tool to unpair the Optane Memory cache device from the backing device being cached, but this can also be performed with the Windows software.

Many of these restrictions are arbitrary and software enforced. The only genuine hardware requirement seems to be a Skylake 100-series or later chipset. The release notes for the final production release of the Optane Memory and RST drivers even includes in the list of fixed issues the removal of the ability to enable Optane caching with a non-Optane NVMe cache device, and the ability to turn on Optane caching with a Skylake processor in a 200-series motherboard. Don't be surprised if these drivers get hacked to provide Optane caching on any Skylake system that can do NVMe RAID with Intel RST.

Intel's latest caching solution is not being pitched as a way of increasing performance in high-end systems; for that, they'll have full-size Optane SSDs for the prosumer market later this year. Instead, Optane Memory is intended to provide a boost for systems that still rely on a mechanical hard drive. It can be used to cache access to a SATA SSD or hybrid drive, but don't expect any OEMs to ship such a configuration—it won't be cost-effective. The goal of Optane Memory is to bring hard drive systems up to SSD levels of performance for a modest extra cost and without sacrificing total capacity.

Introduction Testing Optane Memory
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  • Ratman6161 - Monday, April 24, 2017 - link

    "The test that I would be interested in is if this technology could be an effective cache is speeding up mainstream SSDs."
    That's exactly what I was wondering i.e. if I paired it with my SATA 250 EVO. Or, they have a Crucial MX300 SATA SSD in the test which is an OK lower priced SSD. Given the optane drives are $44 and $77 respectively, if someone had something like the MX300 they might be tempted to pair it with an Optane cache.
    On the other hand you have to have the latest Intel CPU and chipset, and I just jumped ship and went with a Ryzen 5 - so its all academic to me.
    Reply
  • Lolimaster - Wednesday, April 26, 2017 - link

    LTT already did, it's worthless.

    For $77 you're close of a crucial MX300 275GB
    Reply
  • Billy Tallis - Monday, April 24, 2017 - link

    That's the test that was running when it died. Reply
  • Twingo - Monday, April 24, 2017 - link

    Billy, are you expecting to get a replacement so you can conduct all these tests? Reply
  • Billy Tallis - Monday, April 24, 2017 - link

    Yes, the replacement will be delivered tomorrow. But don't expect the follow-up article to be real soon. I also want to update the software on the testbeds and run a reasonably large number of drives through, and do some deeper experimentation with the caching to probe its behavior. Reply
  • beginner99 - Tuesday, April 25, 2017 - link

    Mainstream TLC ssds for sure there will be a speed-up measurable in benchmarks. If we as user would actually notice a difference is a completely other question. Due to KISS instead of spending money on this cache drive, instead just buy a tier higher SSD. If mainstrem choose 960 evo instead or of 960 evo choose 960 pro instead. Reply
  • fallaha56 - Tuesday, April 25, 2017 - link

    absolutely not(!)

    for the reason you said

    the 960 pro offers no meaningful real-world advantage to anyone / 99.9% of users
    Reply
  • Glock24 - Monday, April 24, 2017 - link

    "Only Core 13, 15 and i7 processors are supported; Celeron and Pentium parts are excluded."

    There's a typo or I've never seen those Core 13 and Core 15 CPUs before.

    From the data you showed, I see no real benefit is using Optane as a caching solution vs. using an SSD as boot drive. At least not at that price point.
    Reply
  • Kristian Vättö - Monday, April 24, 2017 - link

    For the full review, could you also monitor DRAM usage? 16GB is not really an entry-level setup, so with that much DRAM Intel's software might be caching to DRAM as well like Samsung's RAPID mode, which would inflate the scores.

    Might also be worthwhile to run at least a couple of the application tests with 4GB/8GB of DRAM to see how things work when caching is done fully by Optane.
    Reply
  • Sarah Terra - Monday, April 24, 2017 - link

    Also optane's incredibly low latency should be tested for real world benefits Reply

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