U.2 NVMe SSDs

What makes a drive U.2

U.2 names a connector and form factor, not a speed. Seagate describes the U.2 connector as the renamed SFF-8639 and notes that NVMe drive bays commonly use four of its high-speed lanes as a PCIe link. Intel's DC P4510, listed here under Intel and Dell part numbers, is specified as U.2 2.5-inch by 15 mm on PCIe 3.1 x4. The KIOXIA CM6-based drives on this page, such as the Dell 7YDNG and P03YC, are U.3 models; the common question below explains how U.3 relates to U.2.

Which servers take U.2 drives

A U.2 drive needs a bay that its backplane wires for NVMe; a SAS/SATA-only bay will not run it. Dell builds the R750 with SAS/SATA, NVMe and mixed front backplanes, so the NVMe count depends on the configuration ordered:

Our R740 and R740xd backplane guide shows how those bays are wired. Each listing states its endurance class; to size one, see how read-intensive, write-intensive and mixed-use drives differ and our DWPD and TBW explainer. NVMe add-in cards and M.2 drives are on NVMe SSDs, and 3.84TB enterprise SSDs compares that capacity across interfaces. An Enterasource warranty backs every SSD; the listing shows for how long.

Common question

Is U.2 the same as U.3?

No. U.3 (SFF-TA-1001) is a tri-mode standard built on the U.2 specification and uses the same SFF-8639 connector, but it defines the links so one bay can take an NVMe, SAS or SATA drive on a universal backplane. KIOXIA states that its U.3 drives are natively backward compatible with U.2 NVMe drive slots, and notes that full interoperability in a tri-mode backplane requires drives and backplanes built to the U.3 specification. Check whether your server's bays are U.2 NVMe or tri-mode before you order.