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Efficient Data Access Management over Flash Memory Storage Systems. Author : Chin-Hsien Wu Presenter : kilroy. Outline. Introduction Related work Motivation Main idea Evaluation Conclusion Q & A.
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Efficient Data Access Management over Flash Memory Storage Systems Author : Chin-Hsien Wu Presenter : kilroy
Outline • Introduction • Related work • Motivation • Main idea • Evaluation • Conclusion • Q & A
Introduction • Flash memory is a popular alternative for the design of storage systems for lots of reasons: • Shock-resistant • Energy-efficient • Non-volatile nature • This thesis focus on NAND flash because of : • NAND flash is more suitable for designing file/storage systems Dr. Fujio Masuoka
Related work • Flash-memory characteristics • Write-once characteristic • Size of Page/block • Cumbrous overhead • Previous Work • Garbage collection • Wear leaving • Energy consumption
Motivation • B-Tree is one of the popular data structures adopted by database systems • However, a direct adoption of B-Tree could exaggerate the overhead of flash management
Main idea • The design and implementation of BFTL:
Main idea (cont.) • Reservation Buffer: • Dirty records should be timely flushed to flash -> “index unit” • Index unit consists of : Original B-Tree component、identifier and op_flag • Note that BFTL use FTL to store index units • Index unit will pack into a logical term “sector”
Main idea (cont.) • The Commit Policy • Index units of the same node could be scattered over sectors
Main idea (cont.) • Node translation table: • Sectors will scatter over flash memory
Evaluation • Experiment setup and performance metrics • 4 MB NAND flash • Reservation buffer size : 60 record • The bound of the lengths of lists in the node translation table : 4
Evaluation(cont.) • Performance of B-Tree Index structures creation • The workloads consisted of insertions only • Inserted 30000 records
Evaluation(cont.) • Performance of B-Tree Index structures maintenance
Evaluation(cont.) • Performance of B-Tree Index structures search
Evaluation(cont.) • The size of reservation buffer and energy consumption issues
Evaluation(cont.) • The size of reservation buffer and energy consumption issues
Conclusion • Original B-Tree not suitable over flash memory • However, a BFTL implement doing well on flash memory