A Distributed Spin-Down Algorithm for an Object-Based Storage Device with Write Redirection

We present a distributed spin-down algorithm for conserving energy in an object-based storage device (OSD) cluster. It differs from traditional spin-down algorithms in that it is cooperative—the decision to spin-down an OSD considers not only its own in- ternal state, but also the state of the other OSDs. Each OSD executes an instance of the spin-down algorithm and adapts to the overall workload. To maximize energy saving, a write request for a spun- down OSD may be redirected to another OSD, and a read request for a redirected object will be redi- rected to the OSD storing that object, thus increas- ing the spin-down duration of a spun-down OSD.