U.2 interface, also known as SFF-8639, combines the characteristics of SATA and SAS interfaces on the device side of U.2. U.2 not only supports the SATA-Express specification, but also is compatible with SAS, SATA, and other specifications. One end of the motherboard is a mini SAS (SFF-8643) interface, and the U.2 cable on the device side is connected to one end of the SATA power supply and one end of the U.2 hard drive data port. Therefore, you can consider it as a four channel version of the SATA-Express interface, with a theoretical bandwidth of 32Gbps, which is no different from the M.2 interface.
The advantage of the U.2 interface is that the interface bandwidth reaches 32Gbps, supports the NVMe protocol, and even improves the power supply capacity, which helps improve SSD performance. However, the downside of the U.2 interface is that it is still an emerging thing. Many motherboards currently do not have the U.2 interface, and there are few consumer grade hard drives with the U.2 interface. Therefore, the U.2 hard drive case on the market is not very common, and there are relatively few SSD equipped with the U.2 interface, So, let me introduce you to a U.2 hdd enclosure.
Unestech 2.5inch Optical Drive Bay U.2 NVMe Extended Storage Hard Drive Case (ST2543U2)
ST2543U2 can install four 2.5-inch U.2 PCIe NVMe SSD in the 5.25-inch optical drive space. It can accommodate up to 15mm U.2 SSD.
In order to make full use of the speed of NVMe SSD, each slot has its own independent MINI SAS HD (SFF-8643) interface, which can play the highest transmission rate of NVMe U.2 SSD of 32 Gbps