WPA: Write Pattern Aware Hybrid Disk Buffer Management for Improving Lifespan of NAND Flash Memory

Recently, consumer electronics devices have started adopting NAND flash memories as their storage units. NAND flash memories are suitable as portable consumer device storages, as they have several advantages such as non-volatility, high density and low power consumption. However, flash memories are difficult to be used directly as storages in consumer devices because of a limited lifespan, which is one of the major drawbacks of NAND flash memory. Therefore, researchers have investigated ways for improving the lifespan of flash memories. In this article, we propose a hybrid disk buffer management policy, which is called the write pattern aware hybrid disk buffer management policy (WPA). The key advantage of WPA is the reduction of write access to the flash-based storage, and this is possible because WPA analyzes the write access pattern that occurred through our pattern aware migration priority by LRU (PaMP-LRU) algorithm and a page eviction list (PEL). We compared our proposed policy with existing hybrid disk buffer policies to evaluate the performance. Experimental results show that under conditions of write-intensive workloads, the performance of WPA is found to be higher than that of other disk buffer policies. In particular, the improvement of WPA hit ratio is 87.6% on average, and WPA reduces block erase counts in flash storage 38.2% on average, and up to 66.8%, resulting in improving the lifespan of NAND flash memory, compared to other disk buffer management policies.