A semi-preemptive garbage collector for solid state drives

Junghee Lee, Youngjae Kim, Galen M. Shipman, Sarp Oral, Feiyi Wang, Jongman Kim

Research output: Chapter in Book/Report/Conference proceedingConference contribution

53 Citations (Scopus)

Abstract

NAND flash memory is a preferred storage media for various platforms ranging from embedded systems to enterprise-scale systems. Flash devices do not have any mechanical moving parts and provide low-latency access. They also require less power compared to rotating media. Unlike hard disks, flash devices use out-of-update operations and they require a garbage collection (GC) process to reclaim invalid pages to create free blocks. This GC process is a major cause of performance degradation when running concurrently with other I/O operations as internal bandwidth is consumed to reclaim these invalid pages. The invocation of the GC process is generally governed by a low watermark on free blocks and other internal device metrics that different workloads meet at different intervals. This results in I/O performance that is highly dependent on workload characteristics. In this paper, we examine the GC process and propose a semi-preemptive GC scheme that can preempt on-going GC processing and service pending I/O requests in the queue. Moreover, we further enhance flash performance by pipelining internal GC operations and merge them with pending I/O requests whenever possible. Our experimental evaluation of this semi-preemptive GC sheme with realistic workloads demonstrate both improved performance and reduced performance variability. Write-dominant workloads show up to a 66.56% improvement in average response time with a 83.30% reduced variance in response time compared to the non-preemptive GC scheme.

Original languageEnglish
Title of host publicationISPASS 2011 - IEEE International Symposium on Performance Analysis of Systems and Software
Pages12-21
Number of pages10
DOIs
Publication statusPublished - 2011
Externally publishedYes
EventIEEE International Symposium on Performance Analysis of Systems and Software, ISPASS 2011 - Austin, TX, United States
Duration: 2011 Apr 102011 Apr 12

Publication series

NameISPASS 2011 - IEEE International Symposium on Performance Analysis of Systems and Software

Conference

ConferenceIEEE International Symposium on Performance Analysis of Systems and Software, ISPASS 2011
Country/TerritoryUnited States
CityAustin, TX
Period11/4/1011/4/12

ASJC Scopus subject areas

  • Software

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