According to a new study, if HDDs continue to progress at their current pace, then in 2020 a two-disk, 2.5-inch disk drive will be capable of storing more than 14 TB and will cost about $40 (today, a typical 500 GB hard drive costs about $100). Although flash memories have also become popular - with advantages such as lower power consumption, faster read access time, and better mechanical reliability than HDDs - the cost per GB for flash memories is nearly 10 times that of HDDs. In addition, flash memory technology will reach technical limits that will prevent its continued scaling before 2020, keeping them from replacing HDDs.
In a study published in a recent issue of IEEE Transactions on Magnetics, Professor Mark Kryder and PhD student Chang Soo Kim of Carnegie Mellon University have investigated 13 up-and-coming NVM technologies to see whether one of them might outperform HDDs on a cost-per-TB basis in 2020. Their results showed that most technologies will probably not be competitive with HDDs or flash memories at that time, except for two potential candidates: phase change random access memory (PCRAM) and spin transfer torque random access memory (STTRAM).
As Kryder and Kim explained, PCRAM is based on the phase change properties of chalcogenide glass. With the application of heat, the glass can switch between two different states (amorphous and crystalline) to be used as a memory. With their small cell size and ability to store multiple bits per cell, PCRAMs have the potential to offer high densities and be cost-competitive with HDDs, but their biggest drawback is that they require somewhat higher power than most other technologies. PCRAMs are already beginning to be marketed by Numonyx Inc., an Intel-ST Microelectronics joint venture, and so are closer to practical realization than STTRAM.
STTRAM, which is similar to magnetic RAM, uses a spin polarized current to write data by reorienting the states of a magnetic tunnel junction between parallel and anti-parallel orientations. In their evaluation, Kryder and Kim found that STTRAMs appear to potentially offer superior power efficiency, among other advantages. If STTRAMs could be improved to store multiple bits per cell, the researchers predict that STTRAMs