Research On The Read Performance And Reliability Of Solid-State Drives

With the advancement of design and manufacturing processes,SSDs(Solid-State Drives)have expanded their storage density and their cost has decreased,making flashbased SSDs have gradually replaced HDDs(Hard Disk Drives)as the dominating computer storage devices.However,as the density of flash memory continues increasing,its reliability,endurance and performance have suffered to varying degrees.The increasing rate of errors has become a major factor affecting the performance of SSDs.Since the previous BCH(Bose-Chaudhuri-Hocquenghem)codes could not accommodate a larger number of errors,LDPC(Low-Density Parity Check)codes has been extensively used in the ECC(Error Checking and Correction)process for SSDs.Although LDPC provides higher fault tolerance,it requires higher decoding latency to ensure data reliability as the increasing number of errors,thus degrading the read performance of the device.Therefore,how to reduce the time consumption in the LDPC decoding process is a key factor to improve the performance of SSDs.Based on the error characteristics of flash memory,this paper proposes a bit-flippingbased data writing scheme called BitFlip and a replication-assisted correction technique for flash memory systems based on deduplication techniques called RECO.Traditional storage schemes have not taken into account the structural characteristics of flash memory internal cells and the data is directly written into the memory,so there are many errorprone states inside the flash memory.BitFlip utilizes the internal structural characteristics of flash memory to analyze the state of each written pag,and then writes the data to the physical flash device after minimizing the number of error-prone states by bit-flipping.When reading data from a flash device,the reduced error-prone state will improve the read performance and prolong the lifecycle of the flash device by reducing the decoding time.Besides,the RECO scheme uses the backup data in the deduplication system to prerecover part of the errors,thus reducing the decoding pressure in the LDPC process.The evaluation results show that BitFlip and RECO significantly reduce the read operation latency and extend the life cycle of flash devices.