A Hybrid Disk-Aware Spin-Down Algorithm with I/O Subsystem Support

To offset the significant power demands of hard disk drives in computer systems, drives are typically powered down during idle periods. This saves power, but accelerates duty cycle consumption, leading to earlier drive failure. Hybrid disks with a small amount of non-volatile flash memory (NVCache) are coming on the market. We present four I/O subsystem enhancements that exploit the characteristics of hybrid disks to improve system performance: 1) artificial idle periods, 2) a read-miss cache, 3) anticipatory spin-up, and 4) NVCache write-throttling. These enhancements reduce power consumption, duty cycling, NVCache block-erase impact, and the observed spinup latency of a hybrid disk, resulting in lower power consumption, greater reliability, and faster I/O.