U.2

U.2 (pronounced "U-dot-2"),^[1] formerly known as SFF-8639, is a computer interface standard used to connect solid-state drives (SSDs) to a computer. It defines the physical connector, electrical characteristics, and supported communication protocols.

U.2 was developed for the enterprise storage market and is designed to support multiple types of drives, including those using PCI Express (typically with NVM Express), as well as SAS and SATA. The interface supports up to four PCIe lanes and two SATA lanes, enabling high data transfer rates while maintaining compatibility with existing drive technologies.