Samsung was a pioneer in introducing 3D NAND Flash memory (they call it V-NAND) in 2013 at the Flash Memory Summit and with shipping products in 2014. The company plans further products increasing the storage capacity in coming years. 3D flash memory stores data in stacks of flash memory cells contained in vertical trenches in the silicon wafer rather than just in an array of flash memory cells on the surface of the NAND flash wafer. Tom Coughlin is general chairman of the Flash Memory Summit and organizer of the 2015 Storage Visions Conference.
3D NAND flash is on every flash memory company roadmap and is a key element in the future development of high capacity flash memory. In 2014 Samsung announced that it would introduce 3-level flash V-NAND flash memory (TLC) to boost flash memory densities even higher.
Intel recently stated that it would supply a 10 TB SSD using 3D NAND produced by Intel Micron Flash Technologies (a partnership between Intel and Micron) by 2016. This product would consist of 32 planar layers (similar to the Samsung V-NAND product currently offering up to 128 Gbit die using TLC flash) with 256 Gbit (32 GB) capacity per die (chip) using 2-level cells (MLC) and 348 Gbit (48 GB) capacity per die using TLC.
Within days of the Intel announcement, SanDisk’s Brian Cox stated that the company currently ships 4 TB SSDs and would ship 8 TB SSDs in 2015 and 16 TB SSDs in 2016. Likely this last product would use TLC 3D NAND. SanDisk is shipping an X300 client SSD using TLC NAND flash memory now. These 10 and 16 TB products in 2016 would greatly expand the storage capacity of flash memory.
HGST has announced a HDD for cold storage applications with up to 10 TB raw capacity. With the introduction of new technologies in HDDs this capacity will increase in coming years and it is possible that with the introduction of Heat Assisted Magnetic Recording or Two Dimensional Magnetic Recording 20 TB HDDs could be possible in two years time. However this is not certain at this time, 12-15 TB with an extension of current magnetic recording technology is more likely. However, even with these capacities the cost of HDDs in terms of HDD storage will likely remain around 7-10X less than that of raw flash memory capacity (in $/TB).
So what will these large SSDs be good for? Probably these drives would not be direct replacements for all HDDs because of the difference in price but there are some interesting applications that expand the ideas for flash memory storage systems. First of all, it is likely that 3D flash with high performance will accelerate the trend for flash memory to replace high RPM HDDs, but this still leaves a lot of applications for higher capacity HDDs
There are a few possibilities for SSDs to replace high capacity HDDs for enterprise applications, based upon discussions with flash memory manufacturers. SanDisk suggests that a flash-based Write Once Read Many (WORM) product using high-density 3D flash and triple (TLC) or even higher number of flash levels could be used for cold storage or archiving applications. At the 2013 Flash Memory Summit Jason Taylor from Facebook described the idea of using low endurance flash memory for archiving photos and other content. Such products could provide higher flash storage capacity while sacrificing endurance (the ability to rewrite the flash memory).
The flash memory storage in a storage system built with this WORM flash memory would still have read speeds that would be higher than HDDs. The price in terms of $/TB could be lower than higher endurance flash memory because of the capacity to endurance trade-off, perhaps bringing the overall raw capacity difference to within 3X that of HDDs. These high capacity flash products would be a type of cold storage and may also require less power than cold storage HDDs to achieve a certain level of performance and thus the overall costs, including operating costs, for storage systems built with these SSDs could get even closer and perhaps less than that of cold storage HDDs.
Higher capacity SSDs could have an important role in the development of a special class of cold (perhaps even archive) storage where data is never or very seldom re-written (WORM storage). The higher performance of the flash memory and a closer $/TB cost to that of capacity HDDs could open up some new market niches for flash memory beyond just storage system performance enhancement. Whether this idea catches on will become clear in time.
