Garbage CollectionMethod using Proxy Block considering Index Data Structure based on Flash Memory

Seon Hwan Kim; Kwak， Jong Wook

Journal of The Korea Society of Computer and Information

Abbr : JKSCI
2015, 20(6), pp.1-11
Publisher : The Korean Society Of Computer And Information
Research Area : Computer Science

Seon Hwan Kim ¹ , Kwak， Jong Wook ²

¹ 영남대학교
² 영남대학교

ABSTRACT

Recently, NAND flash memories are used for storage devices because of fast access speed and low-power. However, applications of FTL on low power computing devices lead to heavy workloads which result in a memory requirement and an implementation overhead. Consequently, studies of B+-Tree on embedded devices without the FTL have been proposed. The studies of B+-Tree are optimized for performance of inserting and updating records, considering to disadvantages of the NAND flash memory that it can not support in-place update. However, if a general garbage collection method is applied to the previous studies of B+-Tree, a performance of the B+-Tree is reduced, because it generates a rearrangement of the B+-Tree by changing of page positions on the NAND flash memory. Therefor, we propose a novel garbage collection method which can apply to the B+-Tree based on the NAND flash memory without the FTL. The proposed garbage collection method does not generate a rearrangement of the B+-Tree by using a block information table and a proxy block. We implemented the B+-Tree and μ -Tree with the proposed garbage collection on physical devices with the NAND flash memory. In experiment results, the proposed garbage collection scheme compared to greedy algorithm garbage collection scheme increased the number of inserted keys by up to about 73% on B+-Tree and decreased elapsed time of garbage collection by up to about 39% on μ-Tree.
KEYWORDS

Flash memory , B+-Tree , Garbage collection , Storage system , Index data structure
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