The most mainstream of the three new form factors is the E1.S, which is the obvious replacement for data center use of M.2 drives.
Just as NVMe freed SSDs from relying on legacy technologies designed for spinning disks, the Enterprise & Data Center SSD Form Factor (EDSFF) family has been purpose-built for NVMe-based drives, whether they contain flash or another storage class memory (SCM) such as Intel Optane.
All of the major SSD makers, including Samsung, are already looking at releasing EDSFF products with support for the new form factors also coming from major hyperscalers including Facebook and Microsoft. Jonmichael Hands, co-chair of the SNIA Solid State Drive Special Interest Group, said the E1.L, E1.S, and E3 designs address the limitations faced by current data center SSD form factors.
The AIC/CEM form factor requires PCIe AIC slots for other devices and has limited hot-plug capabilities while also taking up a great deal of space. Although the 2.5-inch form factor offers many of the desired storage and hot plug features, he said, it’s a mechanical design descended from HDDs and blocks airflow to the hottest components in the server. “They’re not natively designed for flash.”
Although designed for consumer devices, Hands said M.2 devices found their way into the data center because they were small and modular, but they’re low capacity without any hot-plug features and suffer from limited power and thermal scaling for data center use.
The EDSFF family is designed to address the limitations of all three legacy form factors while meeting the demands of today’s data centers, including better thermals, power, and scalability, while also being as future proof as possible to accommodate not only PCIe 4 today but also take advantage of PCie Gen 5 and 6, said Hands. The scalable, thermally efficient, and dense E1.L form factor is designed for high capacity storage with easy serviceability, while the E3 is meant to accommodate NVMe SSD devices with very high capacity and performance are possible due to larger package size, 16 lanes, and increased power. E3 deployments are probably a couple of years away, he said, and longer term will support persistent memory devices as part of upcoming PCIe 5.0 platforms.
The most mainstream of the three new form factors is the E1.S, which is the obvious replacement for data center use of M.2 drives. Hands said the vision was to create a form factor optimized for the NVMe drive design for use across all data center and edge systems to scale as mainstream storage.
Samsung is one company that’s bullish on the E1.S. At the recent OCP Virtual Summit it announced its PM9A3 SSD that uses the form factor with full PCIe Gen 4 support. The company’s E1.S SSD also uses its three-bit V-NAND. Samsung also introduced a comprehensive reference design for its E1.S-based storage system and said in an email interview it’s already seeing interest from major cloud data center operators as the E1.S form factor is optimized for 1U servers, which are common in cloud and edge deployments.
Combining the major benefits of 2.5-inch U.2 SSDs, which are widely considered the optimal storage design for 1U servers today, E1.S provides adequate density levels for both storage and I/O performance in space-constrained environments.
The goal of Samsung’s E1.S form factor reference design was providing the largest capacity and high performance in a single unit, which means implementing cooling methods that enable high-performance and space efficiency, securing power budget and optimizing signal integrity, the company said. Ultimately, it’s trying to increase capacity in a smaller space. For M.2 SSD users, Samsung’s E1.S SSD will expand the SSD power budget, accommodate PCIe Gen 4, and allow datacenter managers to add more SSDs per rack unit.
One appeal of the E1.S form factor is it builds on the lower power consumption capabilities of SSDs, and the higher power budget options that can support improved performance considerations, said Samsung.
The other consideration besides power and performance is the capacity, said Thomas Coughlin, president of research firm Coughlin and Associates, making both E1.L and E1.S likely candidates to become the standard in many data centers. “Both provide more efficient volume metric capacity. By going to higher power single devices that have lot of capacity, the watts per terabyte is less overall,” he said. “They’re running a lot of power through it but actually getting greater energy efficiencies.”
As for the PCIe support going forward, Coughlin said although there is some PCIe Gen 5 out there, it won’t be mainstream until at least 2021. “Gen 4 is the natural focus right now because people are building up their data centers with that.” Even then, he said, it will take time for drives such as Samsung’s E1.S SSD to actually show up in data centers. “The data centers take awhile to actually qualify a new product or a form factor.”
The need for PCIe 4 and better form factors for NVMe SSD is out there, said Coughlin. “Everyone’s working remotely, they’re all using the cloud. The cloud is these big old data centers. Demand is up a lot and it will probably continue to be up.”