Access to Solid State Drives (SSDs) non-Volatile Memory Express (NVMe) is a protocol that permits very high speed. The vital thing to know about NVMe is that it only defines how to read and transfer the data. M.2 based drives and PCIe-based drives can use the NVMe protocol. NVMe is not in comparison to M.2 as M.2 is not a protocol but instead a physical form factor specification. While M.2 is the physical side you can think of NVMe as the logical side.