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It is an important issue to reduce the power consumption of a hard disk that takes a large amount of computer systempsilas power. As a new trend, an NV cache is used to make a disk spin down longer by servicing read/write requests instead of the disk. During the spin-down periods, write requests can be simply handled by write buffering, but read requests are still the main cause of initiating spin-ups because of a low hit ratio in the NV cache. Even when there is no user activity, read requests can be frequently generated by running applications and system services, hindering the spin-down. In this paper, we propose new NV cache policies: active write caching to reduce or to delay spin-ups caused by read misses during spin-down periods and a read miss-based spin-down algorithm to extend the spin-down periods, exploiting the NV cache effectively. Our policies reduce the power consumption of a hard disk by up to 50.1% with a 512 MB NV cache, compared with preceding approaches.
Date of Conference: 12-15 Oct. 2008