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This thesis explores the efficiency of NAND flash memory for storage systems, focusing on the BFTL design to reduce flash management overhead. Evaluation metrics include performance, energy consumption, and suitability for flash.
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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