The Research And Implementation Of Cyclical And Virtual Multi-Controller Technology Of RAID

Nowadays the storage systems are being large-volume,high-performance,high-reliability and scalable,and it is a general trend.RAID(Redundant Arrays of Independent Disks)can improve the I/O bandwidth of the storage layer and ensure the data reliability.However,RAID controllers are becoming the performance bottleneck,and their outage even causes data loss.Therefore,researching on the efficient,reliable and flexible multi-controller technology of RAID has great realistic significance.This thesis proposes the Cyclical Multi-Controller(CMC)based on the virtual dual-controller for RAID systems.Specifically,CMC logically organizes multiple physical controllers as a ring,maps each physical controller to two virtual controllers,and puts two different virtual controllers from two adjacent physical controllers into one virtual dual-controller group.This organization provides good flexibility and scalability as it is easy to reshape the ring when physical controllers join or leave.Besides,to make full use of the calculation,I/O bandwidth and memory resources of each physical controller,the logical disk space is divided by the virtual dual-controller groups and each group manages its corresponding logical volumes independently.CMC also provides a workload-pattern-adaptive logical volumes allocating scheme to achieve load balancing among all the physical controllers.Within one virtual dual-controller group,cached data is duplicated in two separate physical controllers,which ensures valid data not to be lost when a controller fails.A CMC-based RAID prototype is implemented to conduct thorough evaluations.Experiment results show that 1)the CMC-based RAID storage system provides better write performance than Multi-Redundance Multi-Controller scheme by 1.10~1.59;2)the CMC-based RAID storage system gets better degrade write performance than Scale-Out Dual-Controller scheme by 1.09~1.40.