Drive form factors (U.2, M.2, EDSFF)

Drive form factors are the physical shapes an SSD ships in, and the three that matter in servers are U.2, M.2, and EDSFF. M.2 is a small card, about the size of a stick of gum, that plugs directly into a motherboard slot. It carries either SATA or PCIe signaling depending on how it is keyed. U.2 looks like a 2.5 inch hard drive but routes four lanes of PCIe instead of a SATA or SAS link. EDSFF is the newest family, designed specifically for data center NVMe.

M.2 drives are commonly 22 mm wide and 80 mm long, a size written as 2280, with up to four PCIe lanes. U.2 is the standard high-capacity NVMe format in servers, sold from 1.92 TB up to 30 TB and beyond per drive. It hot swaps from the front of a chassis the way a SAS drive does. EDSFF splits into three main sizes. E1.S is a slim card meant to replace M.2 in 1U servers. E1.L is a long ruler-shaped drive built for maximum capacity per slot. E3.S is the 2.5 inch successor now common in new server designs.

Match the form factor to the chassis before ordering, not after. A U.2 backplane will not take an M.2 stick, and most EDSFF bays take neither without a carrier.

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Last verified August 29, 2026.