Replacing hard disk drives with #NAND flash-based solid state drives ( #SSDs ) dramatically improved I/O performance, even over top of the line 15,000 RPM enterprise drives. Access times dropped from 6-12 milliseconds to less than 1ms. For most of us, the move to an SSD felt like getting a whole new computer. But sub-millisecond access times weren't anywhere near what flash drives could do. The problem was the old hardware and software that was optimized over 50 years for HDDs instead of SSDs.
That's where the Non-Volatile Memory express comes in. It is the I/O software stack that is optimized for today's SSDs and future non-volatile storage technologies. NVMe is the new industry standard software interface for PCIe SSDs.
#NVMe eliminates the legacy cruft of HDDs. Since hard drives are so much slower than every other layer of the storage stack - except tape - the software stack makes every effort NOT to go to disk, with layers of caching and other techniques to minimize reads and writes.
Worse, the software stack was so much faster than the disk that little attention was given to optimizing the I/O stack for performance. With SSDs though, the I/O stack went from less than 20 percent of the access time to over 50 percent.
With the advent of PCIe SSDs - I think #Fusion-io, now part of WD, was the first - the much faster PCIe hardware drove the software's contribution to I/O latency up to 80 percent. Clearly, a new I/O stack was needed.
http://www.zdnet.com/article/nvme-the-3-minute-tutorial/
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