Redundant Arrays of Hybrid Disks (RAHD)
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Redundant Arrays of Hybrid Disks (RAHD) is proposed by imitating the RAID levels[1].
A RAHD is a combination of hard disk drives providing ultra-high-density magnetic storage, and flash memory with fast read access. Redundancy is achieved in the same ways as for Redundant Arrays of Inexpensive/Independent Disks (RAID): additional information is written across the array in such a way that failure of part of the storage does not cause loss of data.
RAHD arrays can be designed for two distinct working modes: (1) High-Speed (HS) mode, making maximal use of the speed of flash memory; and (2) Energy-Efficient (EE) mode, designed to minimise power consumption while maintaining performance significantly better than hard disks alone. Trace-driven experimental results show that in the high speed mode a RAHD outperforms purely-magnetic-disk-based RAIDs by a factor of 2.4 - 4; and in the energy-efficient mode a RAHD4/5 can save up to 89% of energy with little performance degradation[1].
