The Future of SSD Form Factors

The adoption of the Enterprise and Data Center Standard Form Factor (EDSFF) has been a hot topic in the enterprise storage industry over the past few years. And now, it seems like OCP is ready to push the adoption further with its new updated specifications during its presentation at this year’s Global Summit. This is exciting news for many reasons, as EDSFF features unique thermal protection capabilities (built-in heatsink and thermal interface material), dynamic capacity ranges, and seamless ease of use.

The adoption of the Enterprise and Data Center Standard Form Factor (EDSFF) has been a hot topic in the enterprise storage industry over the past few years. And now, it seems like OCP is ready to push the adoption further with its new updated specifications during its presentation at this year’s Global Summit. This is exciting news for many reasons, as EDSFF features unique thermal protection capabilities (built-in heatsink and thermal interface material), dynamic capacity ranges, and seamless ease of use.

Form Factor Categories

SSD form factors generally fall into two different standards groups:

• PCI-SIG, which includes the traditional form factors: U.2, M.2 (originated in the client space, and is now being widely used in data centers) and 2.5-inch SSDs and HDDs
• SNIA, which primarily consisted of EDSFF (Enterprise and Data Center Standard Form Factor). This also has its own sub-family of form factors:
  • E1.S (SFF-TA-1006), which features different sizes ranging from 5.9mm to 25mm and is becoming more popular in the hyperscale space; E3 (SFF-TA-1008); and
  • E3 (SFF-TA-1008)
  • E1.L, which currently has 9.5mm and 18mm models.

Examples of E1.S and E1.L form factors

Form Factor Trends in 2026

So what’s in store for these form factors in the near future? Trendfocus, a prominent storage industry market research and consulting firm, released some prediction charts that showed a significant shift to EDSFF for SSD unit and byte volume. About 5 years down the road, M.2 usage is expected to wind down, while EDSFF is driving about half the volume (along with U.2, which still remains relevant) by this time. More specifically, E1.S is doing the majority of this transition.

That said, it does matter a little bit at how you look at the SSD world. As we’re seeing right now, enterprise server vendors like HPE and Dell have put E3.S on their 2023 roadmap for server support. Technically they’ve both announced support for E3.S, but neither is shipping it just yet. Neither have platforms that will support E1.S or E1.L in their mainstream enterprise server platforms.

Lenovo on the other hand has dabbled in E1.S as an option in some of their ThinkSystem servers. The SR630 V2 for instance has a backplane with 16 E1.S SSD slots. Lenovo is also going in on E3.S however in their new servers, it remains to be seen if they’ll continue offering much with the E1.S bays.

That’s mainstream enterprise though. When it comes to cloud providers and hyperscalers, there’s definitely an appetite for E1.S and E1.L systems, as the density becomes very important at scale. All of that being said, it’s likely that EDSFF form factors take over the lion’s share of shipping SSDs in a few years, much as Trendfocus anticipates.

Changes in Specifications

The current specifications have been around for quite some time, so OCP is working on making some important changes.

Looking at EDSFF, the first major update they discussed is thermal characterization, which helps the devices find a common methodology. The problem is, drive manufacturers each have their own versions (a similar issue facing NVMe specifications), so OCP wants everyone to have a common set of rules and specifications. This means manufacturers can simplify their systems.

PCIe 5.0 support

PCIe 5.0 support (for U.2 and M.2) is another major topic OCP is focusing on. We’ve experienced a rapid period of transition lately, moving from PCIe 3.0 to 4.0 and then to 5.0 in a span of just four years (with PCIe 6.0 on the horizon as well). That’s a lot of change for organizations and manufacturers to handle in such a short period of time.

The key to factor factors for OCP is to ensure that signal lanes work correctly (ensuring correct loss/crosstalk specs, etc.), which becomes more important as you increase in frequency. So, much of the work OCP is focused on right now is trying to make sure form factors can support those frequencies.

Changes to E3

Changes to E3 are also currently ongoing. While this is an SSD form factor, one of the things EDSFF has been claiming lately is that they are more than just a storage form factor, so some of the most recent changes have addressed this. For example, the addition of a 4C+ card edge to the connector allows you to use the same slot as the OCP NIC 3.0 and E3, which makes it more interoperable. We’re also seeing some interest from DRAM manufacturers to leverage DRAM over CXL in an SSD-style form factor.

Moreover, OCP added a second 1C connector as well. Instead of a single x8 slot, you can have two x4 connectors next to each other to effectively have an x8 connection. OCP hints at other changes to E3 currently being developed, but these are the most important ones.

I3C Support

The change that is taking up most of their time is I3C support. In a previous presentation roughly a year ago during a composable security architecture presentation, they stressed the need for a faster-than-SMBUS frequency. Interestingly, there was already some talk to move to I3C.

What they ended up deciding on is that I3C basic interface will be optional, while SMBUS will be required to ensure backward compatibility with other form factors. This goes for all form factors.

OCP will be driving this into all form factors. That is, anything PCIe touches will have the ability to have SMBUS or I3C basic.  It’s taking a bit more time than they wanted due to the complexity of things like voltage conversion, but they are nearing the finish line to getting this stuff figured out.

PCIe 6.0 is Coming Soon

Lastly, the looming PCIe 6.0 release. OCP indicates that one of their primary goals is to ensure this interface works effectively with all of the form factors. There are many things to consider here (as they did with PCIe 5.0) and they are especially concerned with eliminating performance loss when connecting to a storage system.

Conclusion

Overall, EDSFF has opened the doors for a lot of new ways of thinking, as it offers a comprehensive range of form factors with advantages over traditional SSD form factors when it comes to capacity, scalability, performance, serviceability, manageability, thermal, and power management.

The storage industry delayed this adoption, however, because many SSD vendors had a hard time indicating where there would be enough volume to warrant an investment. In addition, U.2 has been a safe bet for the enterprise, as it offered enough capacity, and is a tried and tested form factor used everywhere.

Nonetheless, now seems like the time for EDSFF to take a major step as the mainstream choice.

Where to find the Specifications

All of the changes mentioned by OCP are coming soon, so they are asking manufacturers to be ready to implement the latest specifications. These are available at:

• EDSFF: https://www.snia.org/technology-communities/sff/specifications
• U.2 (SFF-8639 module) / M.2: https://pcisig.com/specifications

They also encourage anyone to join SNIA or PCI-SIG in specification development at:

• SNIA: https://www.snia.org/technology-communities/sff/join-sff-ta-twg
• PCI-SIG: https://pcisig.com/membership/become-member
• OCP: https://www.opencompute.org/projects/storage

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