The energy consumed by the memory subsystem is increasing as a fraction of the overall server energy consumption. It is anticipated that upcoming low-power, byte-addressable, persistent-memory technologies, namely Phase-Change RAM (PC-RAM) and Spin-Transfer Torque RAM (STT-RAM), are likely to play a major role in conserving server energy. These technologies are far superior to Flash and, most interestingly, may actually replace DRAM as well.
The research will study hybrid memory subsystems by combining these technologies and DRAM, as well as DRAM-free memory subsystems. The outcomes of this investigation will be: (1) a body of knowledge about PC-RAM and STT-RAM and their potential benefits and limitations; (2) a collection of memory controller and operating system techniques for using these technologies to conserve energy, while bounding performance degradation to user-defined limits; and (3) a simulation and operating system infrastructure that can be used by others in their investigations of memory and energy issues. This work can promote a new direction in memory subsystem design and energ conservation, one that can have a profound impact on the design of future servers.
