RRWL: Round Robin-Based Wear Leveling Using Block Erase Table for Flash Memory

Abstract

SUMMARYIn this letter, we propose a round robin-based wear leveling (RRWL) for flash memory systems. RRWL uses a block erase table (BET), which is composed of a bit array and saves the erasure histories of blocks. BET can use one-to-one mode to increase the performance of wear leveling or one-to-many mode to reduce memory consumption. However, one-to-many mode decreases the accuracy of cold block information, which results in the lifetime degradation of flash memory. To solve this problem, RRWL consistently uses one-to-one mode based on round robin method to increase the accuracy of cold block identification, with reduced memory size of BET, like in one-to-many mode. Experiments show that RRWL increases the lifetime of flash memory by up to 47% and 14%, compared with BET and HaWL, respectively. key words: flash memory, wear leveling, hidden cold block problem, bit array table, block erase table

Novel battery wear leveling method for large‐scale reconfigurable battery packs

“…Dynamic WL handles only frequently accessed data (dynamic data), being a simple to implement yet suboptimal method and making the flash chip's lifetime inversely proportional to the percent of static data. Static WL is applied to the entire memory array and is a more complex method, as it implies moving blocks of static data; it nevertheless offers the best performance in terms of operating time extension 43,44 …”

“…It must periodically reclaim this slack space and repurpose it as free and available pages, through a process called garbage collection. Due to the long erase time, which could degrade overall performance, garbage collection scheduling is still an open issue in the literature [39][40][41][42][43][44] . FTL must then ensure an even allocation of all the memory blocks in order to extend the device's useful life and mitigate the limited lifespan of flash cells.…”

“…Static WL is applied to the entire memory array and is a more complex method, as it implies moving blocks of static data; it nevertheless offers the best performance in terms of operating time extension. 43,44 In a similar way as the FTL can control and disable flash blocks, we have showed in Section 2.2 that reconfigurable battery packs can also control the access to the battery array by selectively disconnecting worn-out batteries to prevent them from further aging. 32 By observing that flash storage and battery storage technologies face similar limitations and challenges in reducing overall degradation and prolonging operational lifetime, we have performed an in-depth comparative analysis of the main features and concepts of the two technologies, in order to identify flash techniques which could be applied to battery packs.…”