What is SATA Express, NVMe, and M.2?

SATA Express – SATA Express, initially standardized in the SATA 3.2 specification, is a newer computer bus interface that supports either SATA or PCIe storage devices. The host connector is backward compatible with the standard 3.5-inch SATA data connector, while also providing multiple PCI Express lanes as a pure PCI Express connection to the storage device. The physical connector will allow up to two legacy SATA devices to be connected if a SATA Express device is not used. The industry is moving forward with SATA Express now rather than SATA 12Gb/s. SATA Express was born because it was concluded that SATA 12Gb/s would require too many changes, be more costly and have higher power consumption than desirable.

For example, 2 lanes of PCIe 3.0 offers 3.3x the performance of SATA 6Gb/s with only 4% increase in power. (2 × PCIe 3.0 lanes with 128b/130b encoding, results in 1969 MB/s bandwidth) 2 lanes of PCIe 3.0 would be 1.6x higher performance and would consume less power than a hypothetical SATA 12Gb/s.

SATA Express is not widely implemented at this time so I am not going to go into much more detail about it. However, keep in mind as of now SATA express SSDs will normally be limited to the chipset and implementation limitations in terms of speed when compared to the potential of true PCIe SSDs.

NVM Express – NVMe or Non-Volatile Memory Host Controller Interface Specification (NVMHCI) is a new and backward-compatible interface specification for solid state drives. It is like that of the SATA modes IDE, AHCI, and RAID, but specifically for PCIe SSDs. It is to support either SATA (I believe specifically SATA Express) or PCI Express storage devices. As you know, most SSDs we use connect via SATA, but that interface was made for mechanical hard drives and lags behind due to SSD’s design being more DRAM like. AHCI has a benefit of compatibility with legacy software. NVMe is much more efficient than AHCI and cuts out lot of overhead because of it.  NVMe has the ability to take more advantage of lower latency and parallelism of CPUs, platforms and applications to improve performance. Multiple OSes have NVMe support already built into them, for example Microsoft added native support for NVMe to Windows 8.1 and Windows Server 2012 R2 and Linux has it built into is kernel as of 2012. Now it’s up to SSD manufacturers to design supporting drives to take advantage of this for their consumer products.

M.2 – Well now that you know what PCIe, SATA, and the different interconnects are, let us go into the new M.2 form factor. I am mentioning the M.2 standard because the Plextor M6e we have for testing is simply a M.2 SSD connected to a PCIe adapter. The M.2 standard is an improved revision of the mSATA connector design. It allows for more flexibility in the manufacturing of not only SSDs, Wi-Fi, Bluetooth, satellite navigation, near field communication (NFC), digital radio, Wireless Gigabit Alliance (WiGig), and wireless WAN (WWAN). On the consumer end, SSDs especially benefit due to the ability to have double the storage capacity than that of an equivalent mSATA device. Furthermore, having a smaller and more flexible physical specification, together with more advanced features, the M.2 is more suitable for solid-state storage applications in general. The form factor supports one SATA port at up to 6Gb/s or 4 PCIe 3.0 lanes at 4GB/s.

source: OverClock