Compatibility Issues

One of the major new features of Intel's Tiger Lake mobile processors is support for PCIe 4.0 lanes coming directly off the CPU. The chipset's PCIe lanes are still limited to PCIe 3.0 speeds, but SSDs or a discrete GPU can now get twice the bandwidth.

This change is relevant because of how Intel's Optane Memory caching software interacts with the system's hardware and firmware. Earlier generations of Optane Memory and Intel's NVMe RAID solutions for their consumer platforms all relied on the NVMe SSDs being attached through the chipset. They used an ugly hack to hide NVMe devices from standard NVMe driver software and make them accessible only through the chipset's SATA controller, where only Intel's drivers could find them. Using chipset-attached NVMe devices with standard NVMe drivers as included in operating systems like Windows or Linux required changing the system's BIOS settings to put the SATA controller in AHCI mode rather than RAID/RST mode. Most of the PC OEMs who didn't provide that BIOS option were eventually shamed into adding it, or only activating this NVMe remapping mode when an Optane Memory device is installed.

For Tiger Lake and CPU-attached NVMe drives, Intel has brought over a feature from their server and workstation platforms. The Intel Volume Management Device (VMD) is a feature of the CPU's PCIe root complex. VMD leaves NVMe devices visible as proper PCIe devices, but enumerated in a separate PCI domain from all the other devices in the system. In the server space, this is a clear improvement as it made it easier to handle error containment and hotplug in the driver without involving the motherboard firmware, and VMD was used as the foundation for Intel's Virtual RAID on CPU (VROC) NVMe software RAID on those platforms. In the client space, VMD still accomplishes Intel's goal of ensuring that the standard Windows NVMe driver can't find the NVMe drive, leaving it available for Intel's drivers to manage.

Unfortunately, this switch seems to mean we're going through another round of compatibility headaches with missing BIOS options to disable the new functionality. It's not currently possible to do a clean install of Windows 10 onto these machines without providing an Intel VMD driver at the beginning of the installation process. Without it, Windows simply cannot detect the NVMe SSD in the CPU-attached M.2 slot. As a result, all of the Windows-based benchmark results in this review were using the Intel RST drivers (except for the Enmotus FuzeDrive SSD, which has its own driver). Normally we don't bother with vendor-specific drivers and stick with Microsoft's NVMe driver included with Windows, but that wasn't an option for this review.

We had planned to include a direct comparison of Intel's Optane Memory H20 against the Enmotus FuzeDrive P200 SSD, but Intel's VMD+RST situation on Tiger Lake prevents the Enmotus drivers from properly detecting the FuzeDrive SSD. On most platforms, installing the FuzeDrive SSD will cause Windows Update to fetch the Enmotus drivers and associate them with that particular NVMe device. Their Fuzion application can then be downloaded from the Microsoft Store to configure the tiering. Instead, on this Tiger Lake notebook, the Fuzion application reports that no FuzeDrive SSD is installed even when the FuzeDrive SSD is the only storage device in the system. It's not entirely clear whether the Intel VMD drivers merely prevent the FuzeDrive software from correctly detecting the drive as one of their own and unlocking the tiering capability, or if there's a more fundamental conflict between the Intel VMD and Enmotus NVMe drivers that prevents them from both being active for the same device. We suspect the latter.

Ultimately, this mess is caused by a combination of Intel and Enmotus wanting to keep their storage software functionality locked to their hardware (though Enmotus also sells their software independently), and Microsoft's inability to provide a clean framework for layering storage drivers the way Linux can (while allowing for the hardware lock-in these vendors demand). Neither of these reasons is sufficient justification for shipping such convoluted "solutions" to end users. It's especially disappointing to see that Intel's new and improved method for supporting Optane Memory caching now breaks a competitor's solution even when the Optane Memory hardware is removed from the system. The various software implementations of storage caching, tiering, RAID, and encryption available in the market are powerful tools, but they're at their best when they can be used together. Intel and Microsoft need to step up and address this situation, or attempts at innovation in this space will continue to be stifled by unnecessary complexity that makes these storage systems fragile and frustrating.

An Alternative: Enmotus FuzeDrive SSD Application Benchmarks and IO Traces
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  • powerarmour - Tuesday, May 18, 2021 - link

    QLC garbage again, I can hardly contain myself.
  • Samus - Wednesday, May 19, 2021 - link

    Understanding QLC's place in the market (cheap bulk flash storage) I'm also struggling to understand who these premium-priced QLC products are for. Seriously who is going to pay 23-25¢/GB for something like this when it's only crutch is high read throughput that has zero real world advantage for virtually all PC users.
  • Wereweeb - Wednesday, May 19, 2021 - link

    These products are both proofs of concept, and an advertising for the importance of Caching/Tiering.

    Enmotus managed to get 3600 TBW out of a 2TB QLC SSD by reducing it's available capacity by a bit and using their software.
  • philehidiot - Wednesday, May 19, 2021 - link

    There is definitely the endurance advantage, but you don't need a commercial product for proof of concept. Indeed, I'd say releasing a commercial product just to prove it can be done where there is no real use for it is a bit daft. Unless they plan to inflict it upon customers in a data collection exercise, using their muscle to force it into laptops. We have already seen the advantages of this kind of tech when smaller SSDs were placed as a cache / tier into HDDs.

    If their plan is to build this into an industrial product, their proof of concept should be a bunch of engineering samples tested for endurance, not a bodged consumer grade product which seems as though it's going to do more to show you can have a very complex and bodged product and it just about compete with what's already established on the market.

    As for advertising, I'd say this is a pretty poor advert. Someone mentioned that Intel's storage division has been held back and it strikes me this is the case. This isn't a new and exciting product, it's two technologies being put together with an inadequate hardware interface and terrible software.

    It has potential, but the people who will accept QLC NAND won't know or care what this is and the people who might benefit from the high DWPD won't touch it with a barge pole.

    This should have stayed in R&D until it could add something to the market.
  • Samus - Thursday, May 20, 2021 - link

    I'll believe it when it's independently tested. No level of software trickery will enable massive gains in TBW. If you fully write to a drive, the physical cells are fully utilized. Sure you can mask this with a large spare area and aggressive wear leveling but even a 2TB QLD SSD with 4TB of physical NAND (so 2TB spare area) will only yield 4x the endurance and that's best case scenario.

    Enmotus can't break the laws of physics with intelligent software unless they've come up with some revolutionary hardware deduplication\compression algorithm that is limiting physical changes to NAND by many orders of magnitude, while also eliminating write amplification that is essential to modern ECC for data integrity.
  • Billy Tallis - Thursday, May 20, 2021 - link

    The key advantage the Enmotus drive has over regular QLC drives is that the static SLC portion can be used for far more P/E cycles. On a regular QLC drive, which blocks are used for the dynamic SLC cache is constantly changing, and the fact that a block that's currently operating as SLC may soon be repurposed as QLC effectively prevents it from being rated for more P/E cycles than QLC usage can permit. But with a large pool of permanent SLC, the drive can safely re-use those cells long past the point where they would be unusable as QLC. 128GiB at 30k P/E cycles can on its own handle more total writes than the drive as a whole is rated for.

    As long as the tiering software does a good job of preventing most writes and write amplification from ever getting to the QLC part of the drive, the endurance rating is completely realistic. The tiering software won't be able to keep the wear confined to the SLC if you are using the drive as a giant circular buffer for video recording or something else that keeps the drive full and constantly modifies all of the data. But most real consumer workloads have a small amount of hot data that's frequently changing and a large amount of cold data that doesn't get rewritten often enough to pose a problem for QLC.
  • Spunjji - Wednesday, May 19, 2021 - link

    Agreed - this would really need to show a serious performance benefit at a similar cost to a TLC drive, or lower cost and similar performance. As it is, it does neither. I'm sure OEMs will lap it up at whatever knockdown price Intel offers it to them to clear the shelves.
  • Spunjji - Wednesday, May 19, 2021 - link

    Derped there and confused the price of the Enmotus with the H20... the Enmotus product really does seem to be in a bad place for price vs. consumer appeal without the benefit of Intel's cosy relationship with OEMs.
  • Morawka - Friday, May 21, 2021 - link

    The Enmotus product is perfect for Chia miners. Plotting on Chia absolutely destroys consumer-grade SSD's. A 980 Pro will get smoked in around 3 months, whereas this Enmotus drive, even though it's pricier, will last 3-5x longer.
  • Billy Tallis - Friday, May 21, 2021 - link

    I think Chia plotting requires more space than the SLC portion of the Enmotus drive, and plotting is an example of the kinds of workloads that would not be handled well by the Enmotus tiering software unless the plotting could fit entirely in the SLC tier.

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