Research On The Cache Algorithm Of Partial Stripe Recovery In Triple Disk Failure Tolerant Arrays

With the development of cloud computing,disk arrays tolerating triple disk failures(3DFTs)are receiving more attention nowadays because they can provide high data reliability with low monetary cost.However,a challenging issue in these arrays is how to efficiently reconstruct the lost data,especially for partial stripe errors(e.g.,sector and chunk errors).It is one of the most significant scenarios in practice.However,existing cache strategies are not efficient for partial stripe reconstruction in 3DFTs,which is because the complex relationships among data and parities are usually ignored during the recovery process.To address this problem,in this paper,we proposed a comprehensive cache policy called Favorable Block First(FBF),which can speed up the partial stripe reconstruction of 3DFTs.FBF investigates the relationships among parity chains via allocating various priorities of shared chunks.Thus in the recovery process,by giving higher priorities to the chunks which are shared by more parities chains,FBF can dynamically hold the significant data in buffer cache for partial stripe reconstruction.Obviously,it increases the cache hit ratio and reduces the reconstruction time.To demonstrate the effectiveness of FBF,we conduct several simulations via Disksim.The results show that,compared to typical recovery schemes by combining with classic cache policies(e.g.,LRU,LFU and ARC),FBF improves hit ratio by up to 2.47× and accelerates the reconstruction process by 14.90%,respectively.Based on that,FBF is also extended to work on multi-disk failure tolerant MDS storage arrays which based on XOR calculation.It's feasibility and effectiveness has been proved by theoretical analysis and experiments.The results show that,FBF has similar characteristic compared with partial stripe recovery on triple disk failure tolerant arrays and the improvement of cache hit ratio can be up to 28.45%.