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PAW: A Pattern-Aware Write Policy for a Flash Non-volatile Cache

Young-Jin KIM, Jihong KIM, Jeong-Bae LEE, Kee-Wook RIM

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Summary :

In disk-based storage systems, non-volatile write caches have been widely used to reduce write latency as well as to ensure data consistency at the level of a storage controller. Write cache policies should basically consider which data is important to cache and evict, and they should also take into account the real I/O features of a non-volatile device. However, existing work has mainly focused on improving basic cache operations, but has not considered the I/O cost of a non-volatile device properly. In this paper, we propose a pattern-aware write cache policy, PAW for a NAND flash memory in disk-based mobile storage systems. PAW is designed to face a mix of a number of sequential accesses and fewer non-sequential ones in mobile storage systems by redirecting the latter to a NAND flash memory and the former to a disk. In addition, PAW employs the synergistic effect of combining a pattern-aware write cache policy and an I/O clustering-based queuing method to strengthen the sequentiality with the aim of reducing the overall system I/O latency. For evaluations, we have built a practical hard disk simulator with a non-volatile cache of a NAND flash memory. Experimental results show that our policy significantly improves the overall I/O performance by reducing the overhead from a non-volatile cache considerably over a traditional one, achieving a high efficiency in energy consumption.

Publication
IEICE TRANSACTIONS on Information Vol.E93-D No.11 pp.3017-3026
Publication Date
2010/11/01
Publicized
Online ISSN
1745-1361
DOI
10.1587/transinf.E93.D.3017
Type of Manuscript
PAPER
Category
Software System

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