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We’ve been hearing a lot about NVMe Solid State Drives (SSD) and we’re just starting to see it introduced by many of the of server and storage vendors. NVMe which stands for Non-Volatile Memory express is a logical device interface specification for accessing non-volatile storage media attached via a PCI Express (PCIe) bus. You can think of NVMe as being the successor of SATA SSD. NVMe is a device interface designed for low latency and parallelism for flash based storage. Traditional spinning disks can have a latency of 140ms, SATA SSD can be around 2ms, while NVMe SSD is at around 0.2ms. Now these numbers may vary based on manufacture, but the idea is that NVMe greatly improves on lowering latency.

I think it’s worth looking back at some of the prior storage interfaces. An interface is simply how a storage device connects to a computer as well as the framework for the software/driver to make it work. For years storage interfaces have been using SCSI and ATA standards. The Advanced Technology Attachment (ATA) uses the Integrated Drive Electronics (IDE) interface. The ATA communication had been parallel until Serial ATA (SATA) was introduced, an evolution of the Parallel ATA physical storage interface. Similarly, SCSI (Small Computer System Interface) is a parallel bus technology. While Serial Attached SCSI (SAS) is an evolution of SCSI. The SAS backplane and controller can also be compatible with SATA drives making it very versatile.

With the advent of Solid State Drives (SSD) there has been a real need to get greater throughput to maximize the full performance of an SSD. As well as the SATA and SCSI was originally designed for spinning disks. The PCI Express / PCIe (Peripheral Component Interconnect Express) interface gets the storage closer to the CPU and removes many of the constraints imposed by the SATA and SAS bottleneck. PCIe is intended for plug-in peripherals, like SSDs and video cards.

I thought it was interesting that the NVM Express group consists of more than 65 companies and is directed by a thirteen-member board of directors, which includes Cisco, Dell, EMC, HGST, Intel, Micron, Microsoft, NetApp, Oracle, PMC, Samsung, SanDisk and Seagate. Even the CompactFlash Association announced that it will be releasing a new memory card specification, CFexpress, which uses NVMe rather than the Advanced Host Controller Interface (AHCI).

One of the hurdles has been the cost of NVMe SSD in comparison of SATA SSD. The first commercially available NVMe drive was the Samsung XS1715 enterprise drive that was announced in July 2013. Then in June of 2014, Intel announced their first NVMe products, which includes the DC P3700 series, the DC P3600 series, and the DC P3500 series. Since then cost has been coming down and large storage companies have been creating arrays that include NVMe SSD’s.

To get the basics of NVMe, a wonderful blog has been written by J. Metz who is a Sr. Product Manager in Cisco's Data Center Group. He has great analogies and lists the difference between NVMe and PCIe. Link to NVMe for Absolute Beginners by J. Metz.

An exciting implementation of NVMe has been the Cisco announcement of NVMe over Fibre Channel in the MDS storage director and UCS C-Series servers. Fibre Channel is the wire in which the NVMe protocol is carried. Link to the Cisco NVMe over FC announcement.

I’ve also been hearing about Pure Storage and their FlashArray//X NVMe all-flash array, but won’t be shipping till early Q2 of 2018. So, I was super excited when I heard that Tegile announced the first mainstream multi-tiered flash array in the storage industry. Many of the tech news picked up on this. https://www.tegile.com/company/news/

Tegile was also fetured in our most recent Fireside Chat. Learn more about Tegile and their  multi-tiered flash array here. 

ATA and SATA Interface Matrix

SCSI and SAS Interface Matrix

 PCIe Bus Matrix

Written By: Marshall Hill, LookingPoint, Inc. Solutions Architect