TLC NAND has made inroads into consumer devices and some data centers, but there is still plenty of room to improve MLC NAND: Micron recently introduced FortisFlash, aimed at balancing endurance and performance for enterprise storage systems.

Micron’s 20nm and 16nm FortisFlash devices come in standard BGA packages of 1 to 16 die stacks and were designed to have better endurance than standard MLC without the usage limitations of Enterprise MLC (eMLC).

Kevin Kilbuck, director of marketing for NAND flash at Micron Technology, said to date, eMLC has been about compromises to improve reliability – essentially trading off performance for more endurance. He said customers want the reliability of eMLC without compromising performance, as well as access to tools so they can tweak the NAND themselves. “That spawned FortisFlash.”

Kilbuck said FortisFlash is faster than consumer MLC and makes use of SLC mode, which Micron has used in its in enterprise SSDs. “We have the same capability in FortisFlash,” he said. “We can use part of the NAND device as SLC.”

But a key part of what makes FortisFlash different is giving customers such as IBM more control by providing them with the tools Micron has internally to help them tune the flash for their usage conditions, said Kilbuck, such as test modes that allow for tweaking flash on the fly. “IBM has access to the knobs.” FortisFlash allows advanced customers to be more proactive in managing the flash, which also improves its lifespan.

FortisFlash can be used in an SSD, said Kilbuck, but it’s better suited for use in something like IBM’s FlashCore technology – IBM is using 20nm FortisFlash in its recently announced FlashSystem V9000 and FlashSystem 900 storage systems.

Michael Kuhn, VP of flash systems at IBM, said it was looking for NAND flash that allowed the company to do some innovation on top to achieve better performance and density without losing the endurance levels of eMLC. IBM integrates flash chips from Micron directly, which allows it to fine tune the NAND for specific customer requirements, as well as optimizing it by using its own error management techniques.

Joe Unsworth, research VP for semiconductors at Gartner, said what’s significant about Micron’s FortisFlash is that it enhances the endurance cycles of conventional consumer-grade MLC, although not as much as an eMLC device, and it does not impact performance as much as eMLC. He said it is a more flexible option for a host customer like IBM that wants to make its own enhancements, although using any NAND flash directly in chip form has benefits and challenges.

One of the benefits is the potential for further optimization of the technology in dense form factors without the mark-up of an external supplier, said Unsworth. However, a certain level of expertise is required from the OEM in these scenarios, as well as a level of cooperation from the NAND supplier. “The perils are that this is quite difficult and missteps can cause one to fall behind the technology,” he said. “It will be a select few that will have the engineering expertise to go direct to the chip level beyond what we have in the market today.”

Planar TLC is not widely deployed in the enterprise, except with a small number of hyper scale customers who have intimate knowledge of their application workloads, said Unsworth. Vendors are continuing to address the challenges inherent to MLC technology, including endurance cycles, enhancing performance and improving data retention while also making NAND more flexible, such as changing states from MLC to SLC. “The key is to provide a common framework that can scale to finer planar process geometries and to 3D NAND.”