Intel on Tuesday introduced its new form-factor for server-class SSDs. The new "ruler" design is based on the in-development Enterprise & Datacenter Storage Form Factor (EDSFF), and is intended to enable server makers to install up to 1 PB of storage into 1U machines while supporting all enterprise-grade features. The first SSDs in the ruler form-factor will be available “in the near future” and the form-factor itself is here for a long run: it is expandable in terms of interface performance, power, density and even dimensions.

For many years SSDs relied on form-factors originally designed for HDDs to ensure compatibility between different types of storage devices in PCs and servers. Meanwhile, the 2.5” and the 3.5” form-factors are not always optimal for SSDs in terms of storage density, cooling, and other aspects. To better address client computers and some types of servers, Intel developed the M.2 form-factor for modular SSDs several years ago. While such drives have a lot of advantages when it comes to storage density, they were not designed to support such functionality as hot-plugging, whereas their cooling is a yet another concern. By contrast, the ruler form-factor was developed specifically for server drives and is tailored for requirements of datacenters. As Intel puts it, the ruler form-factor “delivers the most storage capacity for a server, with the lowest required cooling and power needs”.

From technical point of view, each ruler SSD is a long hot-swappable module that can accommodate tens of NAND flash or 3D XPoint chips, and thus offer capacities and performance levels that easily exceed those of M.2 modules.

The initial ruler SSDs will use the SFF-TA-1002 "Gen-Z" connector, supporting PCIe 3.1 x4 and x8 interfaces with a maximum theoretical bandwidth of around 3.94 GB/s and 7.88 GB/s in both directions. Eventually, the modules could gain an x16 interface featuring 8 GT/s, 16 GT/s (PCIe Gen 4) or even 25 - 32 GT/s (PCIe Gen 5) data transfer rate (should the industry need SSDs with ~50 - 63 GB/s throughput). In fact, connectors are ready for PCIe Gen 5 speeds even now, but there are no hosts to support the interface.

One of the key things about the ruler form-factor is that it was designed specifically for server-grade SSDs and therefore offers a lot more than standards for client systems. For example, when compared to the consumer-grade M.2, a PCIe 3.1 x4-based EDSFF ruler SSD has extra SMBus pins for NVMe management, additional pins to charge power loss protection capacitors separately from the drive itself (thus enabling passive backplanes and lowering their costs). The standard is set to use +12 V lane to power the ruler SSDs and Intel expects the most powerful drives to consume 50 W or more.

Servers and backplanes compatible with the rulers will be incompatible with DFF SSDs and HDDs, as well as with other proprietary form-factors (so, think of flash-only machines). EDSFF itself has yet to be formalized as a standard, however the working group for the standard already counts Dell, Lenovo, HPE, and Samsung as among its promotors, and Western Digital as one of several contributors.


It is also noteworthy that Intel has been shipping ruler SSDs based on planar MLC NAND to select partners (think of the usual suspects - large makers of servers as well as owners of huge datacenters) for about eight months now. While the drives did not really use all the advantages of the proposed standard – and I'd be surprised if they were even compliant with the final standard – they helped the EDSFF working group members prepare for the future. Moreover, some of Intel's partners have even added their features to the upcoming EDSFF standard, and still other partners are looking at using the form factor for GPU and FPGA accelerator devices. So it's clear that there's already a lot of industry interest and now growing support for the ruler/EDSFF concept.

Finally, one of the first drives to be offered in the ruler form-factor will be Intel’s DC P4500-series SSDs, which feature Intel’s enterprise-grade 3D NAND memory and a proprietary controller. Intel does not disclose maximum capacities offered by the DC P4500 rulers, but expect them to be significant. Over time Intel also plans to introduce 3D XPoint-based Optane SSDs in the ruler form-factor.

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Source: Intel



View All Comments

  • petteyg359 - Wednesday, August 16, 2017 - link

    To the contrary, nearly all (every single one I've seen, so "nearly" Matt he incorrect) SATA drives support hot swapping. It's part of the damn protocol. There are *host controllers* that don't support it, but finding those on modern hardware is challenging. Reply
  • Valantar - Wednesday, August 09, 2017 - link

    If this form factor is designed to cool devices up to 50w, and you can stick 32 of them in a 1U server, that sounds like a dream come true for GPU accelerators. Good luck fitting eight 250W (which is what you'd need to exceed the performance of that assuming perfect scaling) GPUs in a 1U server, after all. Reply
  • mode_13h - Wednesday, August 09, 2017 - link

    I'm sad to see the gap between HEDT and server/datacenter widening into a chasm.

    Also, I'm not clear on how these are meant to dissipate 50 W. Will such high-powered devices have spacing requirements so they can cool through their case? Or would you pack them in like sardines, and let them bake as if in an oven?
  • mode_13h - Wednesday, August 09, 2017 - link

    Just to let you know where I'm coming from, I have a LGA2011 workstation board with a Xeon and a DC P3500 that I got in a liquidation sale. I love being able to run old server HW for cheap, and in a fairly normal desktop case.

    I'm worried that ATX boards with LGA3647 sockets are going to be quite rare, and using these "ruler" drives in any kind of desktop form factor seems ungainly and impractical, at best.
  • cekim - Wednesday, August 09, 2017 - link

    12.5mm pitch 9.5mm width - I'm assuming this indicates an air-gap on both sides to allow for cooling.

    As for (E)ATX and EEB MB's I hear ya - ASROCK has some up on their page, but certainly they are not looking like they will be as easy to get as C612 boards were/are.

    I'm not worried about storage tech for consumers, but the CPU divide is definitely widening. Hopefully AMD keeps Intel honest and we start to see dual TR boards that force Intel to enable ECC and do dual i9 systems.

    Software has to get better through, it is still lagging behind and just got roughly 2x the cores consumer software could have ever imagined when they had just started digesting more than 4.
  • surt - Wednesday, August 09, 2017 - link

    According to the article, they specify a pitch between units which would seem to allow for between-blade (ruler) air cooling. Reply
  • ddriver - Thursday, August 10, 2017 - link

    "Or would you pack them in like sardines, and let them bake as if in an oven?"

    That's pretty much the plan. This solution WILL NOT COOL WELL. It will however allow for a substantial amount of heat to sink in, and when it saturates, drives will begin to throttle, killing your performance.

    Additionally, having the drives bake and sweat in heat throughout their entire lifetime will be a real help when designing drives to fail as soon as possible after their warranty period expires. If corporations like intel hate something, that is products which continue being operational for years after their warranty runs out. Rather than people lining up to buy new hardware and generating as much profit as possible.

    Like I already said, it is a decorated money grab. It is possible to have solutions superior to this in every way, while still retaining compatibility with the perfectly adequate 2.5" form factor.
  • flgt - Thursday, August 10, 2017 - link

    The individual drive seems better thermally since all dies have a direct thermal path to the outer cover and the cover provides a lot of surface area for cooling air to flow over. My worry is if this is enough to overcome the total heat density that can now be achieved. If the air flow is front to back the victims may be the circuitry in the back and not the drives since they will see the elevated air temperatures created by the drives. I have to believe someone looked at all that though. Reply
  • HStewart - Wednesday, August 09, 2017 - link

    Well if you combine this with directions of Intel's Compute Card, you see something interesting modular upgrading of components and expansion. But keep in mind the Compute Card are not high end components - but it might point to future plans for Intel - for many Compute Card based server in small amount space.

    My guess this is going quite expensive - but there are many that need this amount storage - but then again at my first job we have a machine with 24M of memory and 1G of storage and that was pretty much unheard of in PC world in 1992.
  • ddriver - Thursday, August 10, 2017 - link

    Let's hear it for convenience.

    The compute card blows up a 2 cent capacitor.

    Your buy another 200$ compute card.

    199.8$ wasted.


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