Today’s enterprise data centers are constantly faced with the unique challenge of balancing power, speed and cooling efficiency with limited space in the server rack. When it comes to storage, the need to find the right balance is even more important. One of the key obstacles to this balance, however, is form factors. Many traditional form factors were designed for hard disk drives (HDDs), not solid state drives (SSDs). As such, they lack the cooling efficiency and storage capacity required for large data centers.
While SSDs are faster and more durable, powerful and energy-efficient than HDDs, the industry had some challenges when enterprises began to switch to SSDs in the beginning. The first SSDs came in 2.5-inch and 3.5-inch Formfaktoren to match the size of HDD enclosures. That made it easy for enterprise to transition to SSDs without having to make major modifications to their infrastructure. However, the mechanical design of 2.5-inch and 3.5-inch enclosures, originally designed for HDDs, actually blocked the SSD’s airflow and restricted its scalability.
SSDs in all shapes, sizes and capabilities
Today, SSDs come in a wide range of form factors, from the original 2.5” and mSATA to U.2 and M.2. The variety allows the users the flexibility to select the right SSDs for their needs, such as size constraints, scalability and high-performance requirements.
All of these SSD form factors were great for general SSD use, but they weren’t optimized for use in enterprise data centers. Organizations needed SSDs that offered greater capacity, scalability, performance, thermal management and energy efficiency to run their most advanced and intensive workloads.
EDSFF responds to enterprise data center needs
About five years ago, a group of experts from the Storage Networking Industry Association created the Enterprise and Datacenter Standard Form Factor, or EDSFF, to address the limitations of current SSD form factors and create better options for enterprises. All EDSFF form factors use NVMe protocol and PCIe interfaces, as well as the same edge connector, pinout and functions. E1 and E3 were the first form factors announced by EDSFF (Figure 1).
Figure 1. EDSFF E1 and E3 form factors, introduced in late 2020
E1.S
The most popular among the variants in the EDSFF family, this form factor’s mechanical design is meant to replace the M.2 drives in the data center. It offers higher density and higher power while retaining a small size. It’s also hot pluggable, which allows IT to replace the drive without switching the system off. Shaped like a stick of gum, the E1.S can fit in 1U space and a 1U storage server can support up to 32 E1.S storage drives. This allows the data center to scale storage capacity and support data and application growth.
E1.L
E1.L is hot pluggable, designed in the shape of a long ruler and optimized for 1U servers. The maximized board space can support more NAND flash packages and enhance cooling efficiency. Typically, organizations used U.2 form factor for large-capacity drives but sometimes the large-capacity U.2 drives were built with two PCBs folded over. The components on the inside were like the middle of a sandwich and the heat from those components was difficult to cool down. E1.L solves the thermal issue by spreading all the area to the surface, along with two thickness options of the metal enclosure (Figure 5). It requires 55% less airflow than the U.2 form factor and the cost of power is reduced significantly as well. E1.L is the densest storage form factor. A single 1U storage server full of E1.L drives can reach a capacity of 1 PB. Enterprise data centers can use E1.L to enhance density while lowering the total cost of ownership (TCO).
Figure 2. E1.L thermal options
E3
The biggest difference between E3 drives and the other form factors in the EDSFF family is shape. E3 looks similar to the traditional 2.5-inch form factor but allows up to x16 PCIe lanes and 70W power. It was created to update and replace the U.2 form factor.
Hot pluggable and optimized for both 1U and 2U servers, E3 comes in four different variations: E3.L, E3.S and either in single (1T) or double (2T) widths, with T standing for thickness (Figure 3). Due to its improved heat dissipation, 2T is typically used for high-power devices that generate more heat, such as computational storage and high-capacity storage.
Figure 3. Variations of E3
E3 is also flexible from the inside. A small-sized E1.S PCBA can fit in an E3 enclosure, which means low-capacity storage with an E3 form factor could leverage E1.S PCBA to lower the cost (Figure 4). Moreover, E3 supports a variety of device types in addition to SSDs, such as persistent memory.
Figure 4. E1.S in E3 enclosure
E2
Introduced at OCP Storage Tech Talk in May 2025, the E2 form factor addresses the widening gap between high-capacity hard drives and high-performance SSDs (Figure 5). It’s designed for the new “warm” data tier, made up of information that’s accessed too often for sluggish HDDs but doesn’t justify the cost of top-tier SSDs.
With support for up to 1 petabyte per drive in a standard 2U server, E2 is engineered for scale. As part of the “Ruler” designation from EDSFF, E2 drives are 7.9” 3” x .4”. A single chassis can house up to 40 drives to deliver a staggering 40 PB of capacity while slashing footprint and power per terabyte. Its hot-pluggable, front-accessible design makes servicing fast and painless, minimizing downtime in demanding environments.
E2 leverages the industry-standard EDSFF connector, ensuring broad compatibility and future-proof scalability. And despite its higher power draw, it delivers significantly better power efficiency per TB than HDDs. This makes it a smarter choice for data centers focused on reducing TCO and energy usage.
Phison SSDs deliver superior performance and capacity
With its commitment to continual advancement of data storage technology, Phison now offers the highest-capacity enterprise Gen5 NVMe drive in the performance-optimized E3.L form factor. The Phison Pascari D205V SSD has a massive capacity of 122 TB, and is helping to demonstrate how next-generation form factors like E3.L are redefining the possibilities of storage density, thermal efficiency, and scalability in enterprise infrastructure.
Figure 5. Phison’s Pascari D205V SSD comes in a variety of form factors
Engineered for high-density, high-performance environments, the E3.L form factor delivers improved airflow and thermal management compared legacy U.2 and U.3 designs. This makes it ideal for AI training clusters, hyperscale environments and dense edge deployments where cooling and physical space are critical constraints.
The Pascari D205V 122 TB SSD delivers unmatched capacity per slot, enabling customers to tackle data-intensive workloads such as AI training and machine learning, real-time analytics, and cloud-scale storage with greater efficiency. This not only reduces total rack space but also lowers operational and energy costs and simplifies infrastructure planning for organizations scaling at the edge or in the data center.
Phison continues to push the boundaries of what is possible in next-generation server architectures today, so you can meet the demands of tomorrow’s enterprise workloads with innovation that scales.
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