M2H: Optimizing F2FS via Multi-log Delayed Writing and Modified Segment Cleaning based on Dynamically Identified Hotness
Lihua Yanga, Zhipeng Tanb, Fang Wangc, Shiyun Tud and Jicheng Shaoe
Wuhan National Laboratory for Optoelectronics, Key Laboratory of Information Storage System Engineering Research Center of Data Storage Systems and Technology, Ministry of Education of China School of Computer Science & Technology, Huazhong University of Science & Technology
alihuayang@hust.edu.cn
btanzhipeng@hust.edu.cn
cwangfang@hust.edu.cn
dtushiyun@hust.edu.cn
eshaojc@hust.edu.cn
ABSTRACT
With the widespread use of flash memory from mobile devices to large data centers, flash friendly file system (F2FS) designed for flash memory features has become popular. However, F2FS suffers from severe cleaning overhead due to its logging scheme writes. Mixed storage of data with different hotness in the file system aggravates segment cleaning. We propose multi-log delayed writing and modified segment cleaning based on dynamically identified hotness (M2H). M2H defines the hotness by the file block update distance and uses the K-means clustering to identify hotness accurately for dynamic access patterns. Based on fine-grained hotness, we design multi-log delayed writing and modify the selection and release of the victim segment. The hotness metadata cache is used to reduce overheads induced by hotness metadata management and clustering calculations. Compared with the existing strategy of F2FS, migrated blocks of segment cleaning in M2H reduce by 36.05% to 36.51% and the file system bandwidth increases by 69.52% to 70.43% cumulatively.
Keywords: F2FS, Segment Cleaning, Hotness, K-Means, Multilog Delayed Writing.
