The JEDEC Solid State Technology Association is looking to update its solid state drive (SSD) standard for the first time in more than four years, and given recent SSD-related technology development, there will be several factors affecting the next iteration of the standard.

Originally published in September 2010, the last update to the JESD218 standard for Solid State Drive Requirements and Endurance Test Method was released in February 2011. As flash becomes more pervasive in data centers, vendors are diversifying their SSD offerings, in part to address different workloads, which JEDEC describes in a separate document.

In a news release, JEDEC said the latest update to JESD218 has been underway for some time and will primarily address improvements in test methodologies to better reflect product expectations, reduce testing options to remove unused methods, and add clarifications to improve the readability and understanding of test methods and artifacts caused by accelerated testing.

JEDEC noted in the release that the standard has been receiving a great deal of attention of late following some misconceptions about retention of data on SSDs, which underscores the need to define “meaningful, real-life endurance and reliability metrics” for SSDs.

Last month, there was much concern about newly-minted SSDs may losing data in “just a few days” when stored in a hot room. The misunderstanding was sparked by a blog that misinterpreted a five-year-old JEDEC presentation.

While improving performance is always a goal of an updated memory technology specifications, usually by double, and reducing power consumption, often by half, endurance is a particular focus of innovation for SSDs. Earlier this year, Micron introduced FortisFlash for enterprise storage systems as an alternative to eMLC, which trades off performance for more endurance. Last year, the company unveiled a client SSD aimed at the mobile computing segment that leverages its new 16nm process technology and with a feature that enables multi-level cell (MLC) NAND cells to act like single-level cell (SLC).

Triple-level cell (TLC) NAND is also becoming more common. To date, it has been primarily used in USB drives, flash memory cards, low-cost smartphones and client SSDs, but it is projected to make further inroads into the data center over the next two years, with MLC still prevalent. Gartner forecasts some TLC adoption by select data center customers, while 3D will be the focal point of NAND technology evolution over the next year.

In March, Micron and Intel said they would be second to Samsung with ultra-dense 3-D NAND flash chips that will sell as chips and in SSDs; Micron will pack 256 Gbits into vertical NAND chips using two-bit per MLC technology and 384 Gbits in TLC versions. Samsung began shipping its 850 series SSDs using 86 Gbit MLC and 128 Gbit TLC chips using vertical NAND last July.

Another factor influencing SSD standards will be NVM Express (NVMe), which is gaining ground as vendors ship new SSDs using the specification for both servers and workstations. NVMe is a standardized register interface, command, and feature set for PCIe-based storage technologies including SSDs, designed specifically for non-volatile memory. It is optimized for high performance and low latency, scaling from client to enterprise segments. The NVM Express Organization, which is overseeing development of standards, announced 1.2 of the NVMe specification last November; the first was released in March 2011.

Last month, JEDEC approved the first standards for support of hybrid DDR4 memory modules. Its JC-45 Committee for Memory Modules developed the non-volatile DIMM (NVDIMM) taxonomy in collaboration with Storage Network Industry Association's NVDIMM Special Interest Group (SIG), a sub-committee of SNIA's Solid State Storage Initiative.

The new standard defines hybrid DDR4 memory modules as those that plug into standard DIMM sockets and appear like a DDR4 SDRAM to the system controller, yet contain non-volatile memories such as NAND flash on the module.

JEDEC's JESD218 Solid-State Drive Requirements and Endurance Test Method defines conditions of use and corresponding endurance verification requirements for client and enterprise SSDs, outlining specific requirements for each. JESD218 also includes an SSD Endurance Rating that represents the number of terabytes written by a host to the SSD, which provides a standard comparison for SSDs based on application class.

By: DocMemory
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