| Summary: | 碩士 === 國立清華大學 === 資訊工程學系 === 104 === Non-volatile random-access memory (NVRAM) becomes a mainstream storage device in embedded systems due to its favorable features, such as small size, low power consumption and short read/write latency. Unlike dynamic random access memory (DRAM), the most NVRAM has asymmetric performance and energy consumption on read/write operations. Generally, on NVRAM, a write operation consumes more energy and time than a read operation. Unfortunately, current mobile/embedded file systems, such as EXT2/3 and EXT4, are very unfriendly for NVRAM devices. The reason is that in order to increase the reliability of file systems, current mobile/embedded file systems employ a journaling mechanism. Although a journaling mechanism raises the safety of data in a file system, it also writes the same data twice during data commitment and checkpoint. Though several related works have been proposed to reduce the size of a write operation, they still cannot effectively minimize the write amplification of a journaling mechanism. Such observations motivate this paper to design a 2-phase write-reduction journaling file system called wrJFS. In the first phase, wrJFS classified data into two categories: metadata and user data. Because the size of metadata is usually very small (few bytes), the metadata will be handled by partial byte-enabled journaling strategy. In contrast, the size of user data is very large relative to metadata; thus, user data will be processed in the second phase. In the second phase, user data will be compressed by hardware encoder so as to reduce the write size, and managed compressed-enabled journaling strategy to avoid the write amplification. The proposed wrJFS is conducted on an EXT3 simulator and runs a series of experiments. The experimental results show that the proposed wrJFS can reduce the size of the write request by 89.7% on average, compared with the original EXT3.
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