Form factors
Consumer/Client Form Factors
| Form Factor | Dimensions (W×L×H) | PCIe Lanes | Typical Use Cases | Notes |
|---|---|---|---|---|
| 2.5” U.2 (SFF-8639) | 2.5” × 15mm thick | x4 | Enterprise servers, workstations | Replaces 2.5” SATA/SAS drives |
| 2.5” U.3 (SFF-8639) | 2.5” × 15mm thick | x4 | Enterprise servers | Tri-mode: NVMe/SAS/SATA on same connector, backward compatible with U.2 |
Enterprise/Data Center Form Factors (EDSFF Family)
The Enterprise and Data Center Standard Form Factor (EDSFF) family was developed by SNIA to replace older form factors (M.2, U.2) with designs optimized specifically for datacenter use. All EDSFF drives share:
- NVMe over PCIe
- SFF-TA-1002 edge connector
- SFF-TA-1009 pinout
- Front-accessible, hot-pluggable, optimized airflow, better thermal management to support high input powers
EDSFF (specifically E3.S and E3.L) are actively replacing U.2 in datacenter deployments. E1.S is up to 3x more thermally efficient than U.2 7mm drives, and E1.L is up to 2x more thermally efficient than U.2 15mm drives.
E1
This is a 1U-optimized ruler form factor, but as best I can tell, it’s a mess of options. The following seem to be common:1
| Form Factor | Dimensions (W×L×H) | PCIe Lanes | Power | Density | Notes |
|---|---|---|---|---|---|
| E1.S | 31.5mm × 111.49mm | x4 | 20W, 25W | Up to 32 per 1U | ”Short” - replaces M.2 in data center, gum stick design |
| E1.L | 38.4mm × 318.75mm | x4, x8 | 25W, 40W | Up to 32 per 1U | ”Long” - ruler form factor, maximum capacity per 1U |
However, E1.S seems to support two lengths (111.49mm and 118.75mm) and five heights (5.9mm, 8.0mm, 9.5mm, 15mm, 25mm).1
E1.L supports only one length (318.75mm) and two heights (9.5mm or 18mm).
E3
This is a 2U-optimized form factor intended to be a replacement for U.2. Both form factors can support either a standard 7.5mm height or a “2T” 16.8mm height.2
| Form Factor | Dimensions (W×L×H) | PCIe Lanes | Power | Density | Notes |
|---|---|---|---|---|---|
| E3.S | 76mm × 112.75mm | x4, x8, x16 | Up to 70W | Up to 46 (7.5mm) or 23 (16.8mm) per 2U vertical | Designed to replace U.2 2.5” drives |
| E3.L | 76mm × 142.2mm | x4, x8, x16 | Up to 70W | Similar to E3.S | Longer version for higher capacity |
E2
As of 2026, this is an emerging standard intended for 2U servers and high capacities per drive.3
| Form Factor | Dimensions (W×L×H) | PCIe Lanes | Power | Density | Target Capacity | Notes |
|---|---|---|---|---|---|---|
| E2 | 76mm × 191.74mm × 9.5mm | x4 (PCIe 6.0+) | Up to 79W | Up to 40 per 2U | 300TB-1PB per drive | ”Ruler” design, supports 64+ NAND packages, targets warm storage tier between HDD and high-perf SSD |
Capacities
| Capacity point | Model | Bits/Cell | Notes |
|---|---|---|---|
| 245.76 TB | Kioxia LC9-series | QLC | PCIe Gen5 |
| 245 TB | Micron 6600 ION | QLC | 1H2026 |
| 256 TB | SanDisk UltraQLC | QLC | 1H2026 |
| 122.88 TB | Solidigm D5-P5336 | QLC | PCIe Gen4 |
| 122.88 TB | Samsung BM1743 | QLC | PCIe Gen5 |
| 61.44 TB | Micron 6550 ION | TLC | PCIe Gen5 |
| 61.44 TB | SanDisk SN655 | TLC | PCIe Gen4 |