NVM Express Solution is Mainstream

Non Volatile Memory (NVM) is a superb technology, at least if you appreciate the physical law behind: storing a data in an embedded location with no physical link, as you charge a cell by influence and read it without physically accessing the stored data. Although the semiconductor industry is building NVM IC for about 30 years now, and we discuss about using NVM storage (Solid State Drive: SSD) in place of Hard disk Drive (HDD) for probably 20 years, it’s only since 5 to 7 years that we consider SSD to be a storage solution complying with economic requirements, at least for enterprise. The cost per GB for SSD has enough decreased over the last decade to become competitive with HDD, even if SSD is still more expensive by a factor of 10.

So, there should be some clear benefits when using SSD, to compensate this price difference… The main is IOPS rate, according with Currie Munce, VP, Research & Advanced Technology, for HGST, a unit of Western Digital, “The performance of an enterprise-class SSD can be about 100x higher for random read/write operations compared to an HDD”. Does that mean that SSD will completely replace HDD for enterprise storage? No, but such an advantage will push to integrate NVM together with HDD to get the best of both, low cost of HDD and high IOPS from SSD.

Increasing adoption of NVM based storage has pushed for the standardization of protocols like Universal flash Storage (UFS) in the mobile industry and NVM Express (NVMe) for enterprise applications. As an IP specialist, that I have learned is that you can evaluate the successful penetration of a technology or protocol by looking at the support from IP vendors, and by the availability of a conformance program. The University of New Hampshire, InterOperability Laboratory, better known by the UNH-IOL acronym, has created the conformance program supporting NVMe. At this point, a chip maker may externally acquire a NVMe IP (NVMe Controller and PCI Express PHY IP) from an IP vendor with a maximum confidence, as far as this IP has passed the UNH-IOL NVMe compliance test. We have just learned that the NVMe Controller IP from Mobiveil has successfully passed this compliance test. As you can see on the picture below, Mobiveil UNEX Controller is listed together with Huawei, Intel, PMC Sierra and Samsung, pretty high profile companies! You may also notice that Mobiveil is the first IP vendor effectively passing the NVMe compliance test…

If you want to understand the role of the NVMe Controller, it’s a good idea to start one level up, or at Subsystem level. This subsystem can be a SSD based memory board for example. If you take a look at the picture below, the subsystem is inserted between the flash IC array on the right side and the PCI Express connection to the host on the left side. The nature of the flash technology is such that the Integrated Flash Controller, interfacing with the Flash IC array, must be complemented with a set of functions: Microcontroller (ARM in this case), DDR3/4 Controller and PHY to access SDRAM external memory and the NVMe Controller itself. You will need to implement all of the above to effectively manage a SSD array, plus a Gen-3 PCIe Controller (and PHY) to build a complete NVMe Subsystem.

The flash technology offer great benefits compared with HDD in term of IOPS, but the physical nature of the flash, specified for a maximum number of Program/Erase (in the range of several 10Ks operations), impose to massively manipulate data and addresses. Manipulating data means that you need to store these data “somewhere”, so the DDR3/4 memory array. The manipulation algorithms are implemented into the Flash Controller and the NVMe Controller, if you can benefit from a dedicated Microcontroller, you will also use it. That’s why a NVMe IP is a complete subsystem. Mobiveil is concentrating on the digital part of the subsystem. Imagine that this NVMe subsystem is implemented into a FPGA device integrating ARM core, DDR3/4 I/Os, ONFI I/O and PCIe gen-3 PHY, (both Xilinx and Altera offer high end families supporting these functions), then you can built a complete NVMe subsystem using Mobiveil IP… almost immediately.

To enable faster product development for its customers, Mobiveil also offers a complete FPGA development platform with a board support package and low-level drivers to validate the solution against their user applications. Thus, Mobiveil’s customer may directly target an FPGA technology, the solution is available off the shelf, and has been not only Silicon proven, but compliant with UNH-IOL. Such a FPGA solution is well tailored for SSD storage in the enterprise market, not so price sensitive but rather performance hungry.

Another market segment adopting NVMe is the mobile segment, smartphone and media tablet. In this case, a customer will most probably target an ASIC technology, due to the price pressure in this market. This chip maker may use his own DDR3/4 or PCIe Controller, nevertheless this customer could source the UNEX Controller and Integrated Flash Controller from Mobiveil, as well as the existing firmware. The advantage for this customer is that he could validate the overal solution by using the above mentioned FPGA development platform, saving design resources (used to build his own development platform) and drastically accelerate Time-To-Market…

Will we, as a end user, massively use SSD equiped devices, PC, Laptops or Media tablets, in the near future ? Probably not before a couple of years, even if you can decide, like I did, to buy a laptop relying on SSD instead of HDD. If the question is : do you, as a end user, use SSD every day ? Then the answer is clearly yes, but you don’t necessarily know that the file you store or download in/from the cloud is already passing through SSD storage system, at some point of the trip.

From Eric Esteve from IPNEST

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