NAND Flash Memory Garbage Collection Policy According to the Ratio of the Hot Pages

Author(s):  
SeokHoon Kang ◽  
HyunYoung Jeong
Author(s):  
Raja Subramani ◽  
Haritima Swapnil ◽  
Niharika Thakur ◽  
Bharath Radhakrishnan ◽  
Krishnamurthy Puttaiah

Author(s):  
Myungsub Lee

In this paper, we propose a block classification with monitor and restriction (BCMR) method to isolate and reduce the interference of blocks in garbage collection and wear leveling. The proposed method monitors the endurance variation of blocks during garbage collection and detects hot blocks by making a restriction condition based on this information. This method induces block classification by its update frequency for garbage collection and wear leveling, resulting in a prolonged lifespan for NAND flash memory systems. The performance evaluation results show that the BCMR method prolonged the life of NAND flash memory systems by 3.95% and reduced the standard deviation per block by 7.4%, on average.


2022 ◽  
Vol 21 (1) ◽  
pp. 1-24
Author(s):  
Katherine Missimer ◽  
Manos Athanassoulis ◽  
Richard West

Modern solid-state disks achieve high data transfer rates due to their massive internal parallelism. However, out-of-place updates for flash memory incur garbage collection costs when valid data needs to be copied during space reclamation. The root cause of this extra cost is that solid-state disks are not always able to accurately determine data lifetime and group together data that expires before the space needs to be reclaimed. Real-time systems found in autonomous vehicles, industrial control systems, and assembly-line robots store data from hundreds of sensors and often have predictable data lifetimes. These systems require guaranteed high storage bandwidth for read and write operations by mission-critical real-time tasks. In this article, we depart from the traditional block device interface to guarantee the high throughput needed to process large volumes of data. Using data lifetime information from the application layer, our proposed real-time design, called Telomere , is able to intelligently lay out data in NAND flash memory and eliminate valid page copies during garbage collection. Telomere’s real-time admission control is able to guarantee tasks their required read and write operations within their periods. Under randomly generated tasksets containing 500 tasks, Telomere achieves 30% higher throughput with a 5% storage cost compared to pre-existing techniques.


2021 ◽  
Vol 11 (14) ◽  
pp. 6623
Author(s):  
Chi-Hsiu Su ◽  
Chin-Hsien Wu

Compared with the traditional hard-disk drives (HDDs), solid-state drives (SSDs) have adopted NAND flash memory and become the current popular storage devices. However, when the free space in NAND flash memory is not enough, the garbage collection will be triggered to recycle the free space. The activities of the garbage collection include a large amount of data written and time-consuming erase operations that can reduce the performance of NAND flash memory. Therefore, DRAM is usually added to NAND flash memory as cache to store frequently used data. The typical cache methods mainly utilize the data characteristics of temporal locality and spatial locality to keep the frequently used data in the cache as much as possible. In addition, we find that there are not only temporal/spatial locality, but also certain associations between the accessed data. Therefore, we suggest that a cache policy should not only consider the temporal/spatial locality but also consider the association relationship between the accessed data to improve the cache hit ratio. In the paper, we will propose a cache policy based on request association analysis for reliable NAND-based storage systems. According to the experimental results, the cache hit ratio of the proposed method can be increased significantly when compared with the typical cache methods.


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