Energy-Efficient Replacement Schemes for Heterogeneous Drive

Much attention has recently been put on the energy-saving scheme for heterogeneous drive(H-Drive) which combines SSD and HDD. This paper focuses on the energy-efficient file buffering schemes for H-Drive while ensuring disks lifespan. We propose a frequency-energy based replacement scheme (FEBR for short) by adapting previous replacement algorithm FBR with the help of an energy-cost model. And based on the sliding-window scheme, we also present a self-adaptive disk power management scheme by taking the disk lifespan into account, which adjusts timeout threshold according to the statistical behavior of user accesses. To explore the applicability of the existing replacement schemes ranging from page-based to file-based buffering scheme, we evaluate their effectiveness on energy-efficiency, performance, and HDD lifetime and compare them with our proposed scheme. With extensive experiments on four real-world file usage traces collected in our office, some useful conclusions are drawn: energy-saving in H-Drive is feasible, it can reach as high as 70%~80%; FBR and its variant FEBR, and GDS are the best ones among all those online buffering schemes evaluated while FEBR has some advantages over FBR and GDS; the proposed self-adaptive disk power management scheme can effectively control the disks lifetime and it is inappropriate to power disk on or off by using those fixed-timeout threshold scheme prevailed previously.