Toshiba and the University of Tokio have presented an interesting technique for improving the write speed of Solid State Drives at last weeks VLSI symposium. The technique is targeted at three-dimensional NAND flash stacks; a method of stacking more NAND flash chips on top of each other to improve storage density and bring down costs.
While flash memory doesn’t need power to retain information, reading and writing data does use a certain amount of power. Currently SSDs include a fixed-capacity power supply that can drive a certain number of read or write channels at the same time. Since each channel needs around 20V to operate when writing data, a typical current-generation drive can power up to 15 channels at a time.
The new power supply includes a “boost converter” that can be switched between low-power and high-power modes. It’s driven by a circuit that monitors the power drawn by the chips; if this exceeds a certain limit the booster is activated, enabling up to 24 write channels to operate simultaneously. This results in a 60% boost in maximum write speed, bringing this up to about 4.2 Gbps (525 MB/s). Obviously the drive will need more power than a traditional SSD when achieving these write speeds; but when the booster is in low-power mode because the drive is idle or there are only a couple of channels active, power usage is up to 32% lower than in a traditional drive.
Toshiba has not provided any information about whether they’ll actually implement this technology, but given the obvious advantages this would offer I’m sure we’ll see an announcement about this within a year.