Optimization And Implementation Of Reading And Writing Strategy Of SSD Based On Erasure Code

Solid State Drive(SSD)has been becoming mainstream storage for its high performance,affordability proportional to its growing storage capacity.However,some inborn characteristics still limit its widespread application:(1)It wears out easily with increasing times of being written/erased.Therefore,SSDs are generally equipped with dedicated Erasure Coding(EC)modules for reliability concerns.However,the EC modules are only statically useful in the sheer scenarios of data loss.In other words,the EC module is never exploited in the regular access situations of dominating frequency,where data is unharmed and intact.(2)Huge latency differences exist among its three basic operations of reading,writing,and erasing,which could lead to performance degradation if there is no proper I/O scheduling.(3)SSD has excellent internal parallelism,which offers a strong possibility to further boost I/O performance if exploited properly.In response to the above problems,the main work of this paper is as follows:This paper proposes Active-Reconstruction-Read,which exploits in a broader sense both its EC module and channel-level parallel-ism in combination to achieve better read performance.It is able to not only guard against data loss but also assist in normal data reads where data is intact,with active use of data reconstruction of the EC module.Aiming at the workload of random small I/O,an SSD optimization of reading strategy based on MDS is proposed.In this strategy,A hybrid Active-ReconstructionRead(ARR)scheme with dynamic judgment is put forward to accommodate read requests with different lengths and states.At the same time,a static strip length setting smaller than the channel number and a data placement strategy with channel wear perception is adopted to promote the performance of the active reconstruction method.Aiming at the workload of sequential large I/O,an SSD optimization of reading strategy based on MSR is proposed.In this strategy,the clay code with the minimum storage overhead and the optimal repair bandwidth and the channel-level parallelism in SSD are utilized,and the response time of the read operation is reduced by reducing the amount of data read from each channel.In this paper,two reading optimization strategies are implemented on the SSDsim simulator.Experiments show that both read optimization strategies can reduce the response delay of reading operations and improve read performance under certain types of workload.