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Flash memory prevalence has reached greater extents with its performance and compactness capabilities. This enables it to be easily adopted as storage media in various portable devices which includes smart watches, cell-phones, drones, and in-vehicle infotainment systems to mention but a few. To support large flash storage in such portable devices, existing flash translation layers (FTLs) employ a cache mapping table (CMT), which contains a small portion of logical page number to physical page number (LPN-PPN) mappings. For robustness, it is of importance to consider the CMT reconstruction mechanisms during system recovery. Currently, existing approaches cannot overcome the performance penalty after experiencing unexpected power failure. This is due to the disregard of the delay caused by inconsistencies between the cached page-mapping entries in RAM and their corresponding mapping pages in flash storage. Furthermore, how to select proper pages for reconstructing the CMT when rebooting a device needs to be revisited. In this study we address these problems and propose a fault tolerant power-failure recovery mechanism (FTRM) for flash memory storage systems. Our empirical study shows that FTRM is an efficient recovery and robust protocol.

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Flash memory is widely used in solid state drives (SSD), smartphones and so on because of their non-volatility, low power consumption, rapid access speed, and resistance to shocks. Due to the hardware features of flash memory that differ from hard disk drives (HDD), a software called FTL (Flash Translation Layer) was presented. The function of FTL is to make flash memory device appear as a block device to its host. However, due to the erase before write features of flash memory, flash blocks need to be constantly availed through the garbage collection (GC) of invalid pages, which incurs high-priced overhead. In the previous hybrid mapping schemes, there are three problems that cause GC overhead. First, operation of partial merge causes more page copies than operation of switch merge. However, many authors just concentrate on reducing operation of full merge. Second, the availability between a data block and a log block makes the space availability of the log block lower, and it also generates a very high-priced operation of full merge. Third, the space availability of the data block is low because the data block, which has many free pages, is merged. Therefore, we propose a new FTL named DSFTL (Dynamic Setting for FTL). In this FTL, we use many SW (sequential write) log blocks to increase operation of switch merge and to decrease operation of partial merge. In addition, DSFTL dynamically handles the data blocks and log blocks to reduce the operations of erase and the high-priced operation of full merge. Additionally, our scheme prevents the data block with many free pages from being merged to increase the space availability of the data block. Our extensive experimental results prove that our proposed approach (DSFTL) reduces the count of erase and increases the operation of switch merge. As a result, DSFTL decreases the garbage collection overhead.