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Design Tradeoffs for SSD Performance

Design Tradeoffs for SSD Performance. Nitin Agrawal, Vijayan Prabhakaran, Ted Wobber, John D. Davis, Mark Manasse, and Rina Panigrahy USENIX 2008. 72081085 김유미 단국대학교 대학원 컴퓨터학과. Authors. Vijayan Prabhakaran Ted Wobber John D. Davis Mark Manasse Rina Panigrahy. Nitin Agrawal.

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Design Tradeoffs for SSD Performance

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  1. Design Tradeoffs for SSD Performance Nitin Agrawal, Vijayan Prabhakaran, Ted Wobber, John D. Davis, Mark Manasse, and Rina Panigrahy USENIX 2008. 72081085 김유미 단국대학교 대학원 컴퓨터학과

  2. Authors Vijayan Prabhakaran Ted Wobber John D. Davis Mark Manasse Rina Panigrahy Nitin Agrawal

  3. SSD의 등장 Why? “Solid-state disks (SSDs) have the potential to revolutionize the storage system landscape.”

  4. SSD • Solid State Drive의 약자 • 반도체를 이용하여 정보를 저장하는 장치 • High: performance, power savings, reliability

  5. HDD vs. SSD

  6. HDD vs. SSD 거의 모든 면에서 SSD가 하드 디스크비해 우수

  7. SSD 가격

  8. Industry Trends • Consumer portable storage • Laptop disk replacements • Enterprise/database accelerators

  9. SSD는 Flash memory 기반 • Flash Memory • 장점 • 빠른 랜덤 접근 가능 • 크기 작음 • 전력소모 적음 • 충격과 진동에 강함 • 단점 • Overwrite 불가 • 새로운 데이터를 기록하기 위해서 먼저 실제 기록한 데이터보다 큰 영역에 대해 지우기 작업(모든 내용1로) 수행해야 함 • 각 Block마다 지우기 횟수 제한있음 SSD 내부에 사용된 삼성전자 NAND Flash 메모리

  10. Target Flash Internal • Samsung’s K9XXG08UXM 4 GB Single Level Cell (SLC) package

  11. SSD Architecture

  12. Challenges • Non‐overwrite • Erase before writing • Limited serial bandwidth • Limited lifetime(erasures) : allocation & layout : interleaving : wear‐leveling

  13. SSD Design Issue • Data placement • Needed for wear leveling and load balancing. • Parallelism • Single flash chips aren’t very fast so they need to work together. • Write ordering • Small random writes are a killer. • Workload management • Performance is highly workload-dependent.

  14. Simulator • Built an SSD simulator • Extended from CMU’s DiskSim Operational attributes of the Samsung 4GB flash memory.

  15. SSD Performance

  16. Workloads • TPC-C • Exchange • IOzone • Postmark

  17. Limited serial bandwidth • Interleaving

  18. Interleaving

  19. Interleaving Within Package

  20. Copy-back

  21. Copy-back vs. Inter-plane Transfer

  22. Overprovisioning

  23. Tradeoff Summary

  24. Wear-leveling • Goal: use all blocks uniformly Bad!! Good!!

  25. Limited Erase Cycles

  26. Wear-leveling Simulation

  27. Conclusion • Understand design tradeoffs for SSD performance • Trace‐based simulator • Tradeoff across all dimensions • Architecture, Algorithms, Policies, Workload

  28. Q& A

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