Solid State Drive Form Factors

Solid-state drives (SSDs) are commonly used in client, hyperscale and enterprise compute environments.  They typically come in three flavors:  NVMe, SAS, and SATA. Since SSDs are made from flash memory, they can be built in many different form factors. This resource guide is designed to provide information on the most common and current SSDs in their various form factors. In addition to the form factor dimensions, information such as use case, interface, protocol, and mechanical/electrical and connector specifications are provided.

Click on the names below to learn more about the many different SSD sizes and formats in a variety of form factors: 


EDSFF

EDSFF stands for Enterprise and Data Center SSD Form Factor. The family of specifications were developed by a group of 15 companies working together to address the concerns of data center storage, and are now maintained by SNIA as part of the SFF Technology Affiliate Technical Work Group (SFF TA TWG).

EDSFF offers a dynamic range of form factors that have advantages vs the incumbent SSD form factors in capacity, scalability, performance, serviceability, manageability, thermal and power management. Today all the EDSFF family of form factors share the same protocol (NVMe), the same interface (PCIe), the same edge connector (SFF-TA-1002), the same pinout and functions (SFF-TA-1009). Infrastructure, especially test infrastructure, can be developed to support multiple EDSFF form factors. Learn more about the EDSFF family.


E1.L, EDSFF 1U Long

E1.L is a form factor that was developed to maximize capacity per drive and per rack unit in a 1U server or storage array (JBOD, JBOF), with superior manageability, serviceability, and thermal characteristics vs traditional form factors that were designed for rotating media. There are options for x4 or x8 lanes of PCIe while fitting vertically in a 1U chassis to allow for scalable bandwidth per drive, as well as options for 9.5 or 18mm heat sinks for various power and thermal environments (25W and 40W respectively). It improves data center serviceability, and is designed to be hot pluggable and front access serviceable with LEDs built into an integrated enclosure.

Use Cases

E1.L is optimized for high-capacity and dense storage use cases. High capacity per rack unit can improve data center TCO by offering storage consolidation and more power efficient storage (TB/W).

Dimensions

Type Width Length Thickness
E1.L 9.5mm up to 25W - 38.4mm 318.75mm 9.5mm
E1.L 18mm up to 40W - 38.4mm 318.75mm 18mm

Mechanical/Electrical Specification:

Connector Specification:

Interface:

  • PCIe
  • NVMe

E1.S, EDSFF 1U Short

E1.S is a flexible, power efficient building block for hyperscale and enterprise compute nodes and storage. The M.2 110mm was popular in hyperscale data centers due to the low-cost structure, flexibility, and scalability of multiple drives per server – but had challenges in hotplug / serviceability, thermals and overheating, and scaling to high capacities. E1.S solves those problems while maintaining the small form factor; E1.S is a small form factor being just a bit longer than M.2 but wider to accommodate more media (NAND) packages for increase capacity per drive. It fits vertically in a 1U chassis, similar to E1.L. The specification for E1.S 5.9mm has four standard mounting holes for heat sinks or carriers.

Different variants of E1.S offer improved flexibility for power, performance, scalability, and thermal efficiency. The latest version of E1.S offers a new optional symmetrical enclosure of 9.5mm width (similar to E1.L) that allows scalability up to 20W and x8 PCIe if required. Mainstream SSDs are still expected to be only PCIe x4, but the PCIe x8 support in the form factor allows use of other devices that need higher bandwidth.

The 15mm and 25mm asymmetrical enclosures offers a tradeoff of fewer drives per rack unit but improved power and performance per drive. At similar power per drive, the 15mm and 25mm enclosures offer improved cooling and thermal performance, decreasing the required airflow.

 

Use Cases

  • Cloud compute servers
  • OEM 1U performance server

Dimensions

Type Width Length Thickness
E1.S 5.9mm 31.5mm 111.49mm 5.9mm
E1.S 8mm heat spreader 31.5mm 111.49mm 8.01mm
E1.S Symmetric Enclosure 33.75mm 118.75mm 9.5mm
E1.S Asymmetric Enclosure 33.75mm 118.75mm 15mm
E1.S Asymmetric Enclosure 33.75mm 118.75mm 25mm

Mechanical/Electrical Specification:

Connector Specification:

Interface:

  • PCIe
  • NVMe

E3, EDSFF 3 in Media Device

E3 has various options for length and height meant for 2U vertical orientation or 1U horizontal, but fits vertically and is optimized for mainstream 2U servers. Like the E1 family, they are hot pluggable / serviceable and higher capacity per drive vs U.2. There are two options for width, 7.5 and 16.8mm thick to maximize drives per system or allow for higher power devices. The device maximizes space utilization in a 2U chassis by increasing the board real estate to allow for more media sites and packages, up to 50% increase vs U.2 single PCB designs. The long term outlook is that E3 could be the true successor to U.2 in 2U servers. E3 will offer more power and performance vs. U.2 SSDs, better signal integrity at higher PCIe speeds (PCIe 5.0 and beyond), better cooling, and reduced system infrastructure cost.

Where Used

  • The primary usage is SSDs, but E3 is big enough to accommodate a broader range of device types.
  • The E3 form factor allows for x4, x8, or x16 PCIe host interface.

Dimensions

Type Width Length Thickness
E3.S 7.5mm 76mm 104.9mm 7.5mm thickness
E3.S 16.8mm 76mm 104.9mm 16.8mm
E3.L 7.5mm 76mm 142.2mm 7.5mm
E3.L 18mm 76mm 142.2mm 16.8mm

Mechanical/Electrical Specification:

Connector Specification:

Interface:

  • PCIe
  • NVMe
  • Upcoming interfaces: Gen Z, CXL, OCP…

M.2

M.2 is a form factor for internally mounted SSDs.  Formerly known as Next Generation Form Factor (NGFF), M.2 supports PCIe, SATA and USB interfaces and comes in various widths and lengths.  It also has keying notches on the edge connector to designate various interface or PCIe lane configurations.

Dimensions

To view a visual representation of M.2 form factor dimensions, click here.

Name Description Use Cases Dimensions (W x L x H, mm)
16mm x 20 mm x2 or x4 lanes PCIe running the NVMe command set, surface mounted or on 22x30 M.2 PCB.  Capacities up to 1TB Mobile/Tablet/Laptop 16.15 x 20.15 x 1.3
22mm x 30mm x2 or x4 lanes PCIe running the NVMe command set. May be BGA mounted on M.2. Capacities up to 1TB. Mobile/Tablet/ Laptop/PC boot/ Server boot 22.15 x 30.15 x 2.23

22mm x 80mm

x4 lanes PCIe running the NVMe command set. Capacities up to 4TB.

Laptop/PC/ Server or Hyperscale data/ Server boot

22.15 x 80.15 x 2.23

22mm x 110mm

x4 lanes PCIe running the NVMe command set. Capacities up to 8TB. 

PC boot and Data/ Server or Hyperscale data

22.15 x 110.15 x 3.88

Mechanical/Electrical Specification:

Connector Specification:

Interface:

  • SATA
  • NVMe/PCIe

2.5-inch (U.2)

The 2.5-inch form factor is the most common deployment of an SSD.  It leverages the server and storage systems built around hard disk drives (HDD).  All interfaces have 2.5-inch form factor options.  This form factor is associated with the term U.2 and is sometimes referred to as the U.2 form factor.  U.2 is somewhat defined as compliance with the PCI Express SFF-8639 Module specification, and no longer typically references SAS or SATA SSDs.

Name Description Use Cases Dimensions (W x L x H, mm)
2.5-inch (7 mm) Typically 6Gb/s x4 NVMe, slim form factor, capacities up to 3.84TB NVMe interface, PC or Server, Hyperscale environments

69.85 x 100 x 7

2.5-inch (7 mm)

Typically 6Gb/s SATA, slim form factor, capacities up to 3.84TB

SATA interface, PC or Server, Hyperscale environments

69.85 x 100 x 7

2.5-inch (15 mm) Typically 12Gb/s x4 NVMe, dual-port support, capacities up to 30.72TB NVMe interface, Server or Storage, Enterprise environments

69.85 x 100 x 15

2.5-inch (15 mm)

Typically 12Gb/s SAS, dual-port support, capacities up to 30.72TB

SAS interface, Server or Storage, Enterprise environments

69.85 x 100 x 15

Mechanical/Electrical Specification:

Connector Specification:

Interface:

  • NVMe
  • SATA
  • SAS

Add-In Card (AIC)

An Add-in Card (AIC) is a solid-state device that utilizes a standard card form factor such as a PCIe card. The AIC would usually use an interface such as PCIe, or possibly a mezzanine card of a standard form type.  Given the larger physical size over an SSM, the AIC would typically have larger capacity and potentially higher performance.  In addition, the larger size allows for the potential to add computational function to the storage device. Because of the versatility of the form factor, the AIC is a form factor that likely will constantly evolve for solid-state storage.

Name Description Use Cases Dimensions (in/mm)
Full Height PCIe Enterprise and cloud deployments, server deployments, large capacity, additional processing for security, storage functionality, and/or future expansion. Support of higher range of power options.

6.6 in/167 mm

Half Height

PCIe

Enterprise and cloud deployments, server deployments, large capacity, additional processing for security, storage functionality, and/or future expansion. Support of higher range of power options.

4.3 in/ 111 mm

Low Profile PCIe Enterprise and cloud deployments, server deployments, large capacity, additional processing for security, storage functionality, and/or future expansion. Support of higher range of power options.

2.5 in/64 mm

Full Length PCIe Enterprise and cloud deployments, server deployments, large capacity, additional processing for security, storage functionality, and/or future expansion. Support of higher range of power options. 12.2 in/312 mm

Half Length

PCIe

Enterprise and cloud deployments, server deployments, large capacity, additional processing for security, storage functionality, and/or future expansion. Support of higher range of power options.

6.6 in/167 mm

Actual SSC dimensions may be less, dependent on design.

PCIe cards can also come in multiple widths. Such a configuration allows mating with adjacent motherboard connectors, enabling increased performance by supporting more than 16 PCIe lanes.

Mechanical/Electrical Specification:

  • The PCI SIG defines form factor sizes.

Interface:

  • NVMe
  • PCIe
  • The Compute Express Link (CxL) standard being defined is likely to allow for new forms of storage and computation in an AIC