Author : Chin-Hsien Wu

Presenter : kilroy

OutlineIntroductionRelated workMotivationMain ideaEvaluationConclusionQ & A

IntroductionFlash memory is a popular alternative for the

design of storage systems for lots of reasons:Shock-resistantEnergy-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 workFlash-memory characteristics

Write-once characteristic Size of Page/blockCumbrous overhead

Previous WorkGarbage collection Wear leavingEnergy consumption

MotivationB-Tree is one of the popular data structures

adopted by database systemsHowever, a direct adoption of B-Tree could

exaggerate the overhead of flash management

Main ideaThe 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_flagNote that BFTL use FTL to store index unitsIndex 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

EvaluationExperiment setup and performance metrics

4 MB NAND flash Reservation buffer size : 60 recordThe bound of the lengths of lists in the node

translation table : 4

Evaluation(cont.)Performance of B-Tree Index structures

creationThe workloads consisted of insertions onlyInserted 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

ConclusionOriginal B-Tree not suitable over flash

memoryHowever, a BFTL implement doing well on

flash memory