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SSD Cache for RAID: Integrating Data Caching and Parity Update Delay

RAID를 위한 SSD 캐시: 데이터 캐싱과 패리티 갱신 지연 기법의 결합

  • 하성태 (서울시립대학교 컴퓨터과학부) ;
  • 이동희 (서울시립대학교 컴퓨터과학부)
  • Received : 2017.03.15
  • Accepted : 2017.04.03
  • Published : 2017.06.15

Abstract

In enterprise environments, hybrid storage typically utilizes SSDs over disk-based RAID. Typically, SSDs over RAID are used as the data cache. Recently, the LeavO caching scheme was introduced to reduce the parity update overhead of the underlying RAID. In this paper, we combine the data caching and LeavO caching schemes and derive cost models of the combined cache to determine the optimal data and LeavO cache sizes. We also propose the Adaptive Combined Cache that dynamically adjusts the data cache and LeavO cache sizes for evolving workloads. Experimental results show that the performance of the Adaptive Combined Cache is significantly superior to that of the conventional data caching scheme and is comparable with that of the off-line optimal scheme.

디스크 기반 RAID와 SSD를 결합한 하이브리드 스토리지가 기업 환경에서 널리 이용되고 있다. RAID 상단의 SSD는 주로 데이터 캐시로 사용된다. 최근 SSD를 사용하여 패리티 갱신 비용을 감소시키는 LeavO 캐시 기법이 제안되었으며, 본 논문에서는 데이터 캐시와 LeavO 캐시를 결합한 혼합 캐시기법을 제안한다. 특히 SSD 공간을 데이터 캐시와 LeavO 캐시, 두 영역으로 최적으로 분할하기 위해 비용 모델을 도출하고, 워크로드에 따라 두 영역의 크기를 동적으로 조절하는 적응형 혼합 캐시 기법을 개발하였다. 실험 결과에 따르면 적응형 혼합 캐시 기법은 기존 데이터 캐시 기법에 비해 좋은 성능을 보이며, 오프라인 최적 기법과 대등한 성능을 보인다.

Keywords

Acknowledgement

Supported by : 서울시립대학교

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