A team of researchers led by Ken Takeuchi, professor of Chuo University's Department of Electrical, Electronic and Communication Engineering in Japan, have unveiled a prototype solid-state drive (SSD) architecture which combines NAND flash with ReRAM components to boost performance while cutting power draw by as much as 93 per cent.

The team's research, due to be formally announced at the Symposium on Very Large Scale Integrated (VLSI) Circuits in Hawaii today, has been reported by Japanese technology site Tech-On, and the claims are nothing short of impressive: the prototype device writes 11 times faster than standard multi-level cell (MLC) NAND flash components while reducing power draw to just 7 per cent of the competing technology.

The system works in a similar way to current hybrid hard drives: where a hybrid hard drive combines a slow but capacious spinning disk with a small but speedy SSD cache area, Takeuchi's design combines a large SSD component with a smaller module constructed from resistive memory (ReRAM.)

According to the team's figures, a standard MLC NAND flash module can record data at a rate of around 4.2MB/s. A MLC NAND flash module combined with a ReRAM module and a trio of clever algorithms - including one designed to prevent data fragmentation - results in a speed boost to 46MB/s - and a drop in power from 0.12 joules per megabyte to 0.0079J/MB. If that wasn't impressive enough, it's claimed that a ReRAM-and-MLC hybrid device would feature a lifespan some seven times greater than that of MLC storage alone.

The massive performance boosts are aided by the capabilities of ReRAM, which include read latency of less than 3μs per sector compared to 85μs per page for MLC, write latency of less than 3μs per sector compared with 400μs per page for the fastest single-level cell (SLC) flash, no need to erase data thanks to partial write or overwrite support, 512-byte sector addressing to NAND flash's 16KB page addressing, and low voltage support to 1.2V compared to NAND flash's 1.8V.

Sadly, Takeuchi and his team are silent regarding commercial availability of the MLC-and-ReRAM components, but with numerous companies already investigating commercialisation of ReRAM parts - including memory giant Elpida - it surely can't be too far away.


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