The new NVM Express 2.0 has been released and with it a surprise: The\u00a0non-volatile memory express protocol\u2014best known for handling SSD speeds\u2014is now offering full-blown support for traditional hard-disk drives.\nThis is quite unexpected because SSDs are orders of magnitude faster than traditional HDDs.\n\nThe first flash-based SSDs used SATA\/SAS physical interfaces borrowed from existing hard drive-based enterprise server\/ storage systems. However, none of these interfaces and protocols were designed for high-speed storage media and the SATA\/SAS bus became a bottleneck for the much faster SSD.\nThe initial fix was SSDs on a PCI Express (PCIe) card. While much faster, PCIe was also proprietary and meant as a point-to-point transfer. A PCIe SSD in one server could not be directly accessed by any other server, it had to go through the system bus, adding all kinds of latency.\nNVMe was soon developed, offering a highly scalable storage protocol that connects the host to the memory subsystem. This made SSDs accessible to computers\/servers beyond the one where they were physically located. NVMe wasn\u2019t meant as a replacement for PCIe\u2014it ran on top of it\u2014using PCIe\u2019s much greater speed than SATA.\nSo it\u2019s a big surprise that NVMe 2.0 added support for \u201crotating media,\u201d as the spec puts it. A current 7200-r.p.m. hard drive cannot fully saturate current SATA 3.0 connections, let alone PCIe Gen 3, which is twice as fast as SATA 3. Now PCIe Gen 4 is coming to market, with double the throughput of Gen 3.\nHDD won\u2019t die anytime soon\nEven as we move to a SSD world, hard drives have their place, namely, large capacity.\u00a0 Sure there are 8TB SSD. They are also insanely expensive. HDDs are reaching the 20TB barrier for a lot less than an equivalent SSD, so it\u2019s unlikely BackBlaze or other cloud-storage firms will move quickly to SSDs.\nAnd while HDDs are slow, don\u2019t count that part out, either. For example, Seagate\u2019s Mach.2 HDD\u00a0uses two separate drive-head mechanics do double read\/write activity. Seagate recently announced that its Mach.2 hard drives can reach up to 524MB\/s of I\/O, which is SATA SSD speed. Mach.2 is sampling to key customers, so general availability has to be approaching.\nThe SATA spec has not been updated in 12 years, which in the tech industry qualifies it as abandoned. By moving HDDs to PCIe\/NVMe, the SATA and SAS buses can be effectively removed from the motherboard and free up space. That won\u2019t happen overnight, of course, but it could and should happen.\nStorage vendors argue back and forth on whether hybrid-array or all-flash will dominate the data center. The NVMe 2.0 spec appears to be preparing for either eventuality.