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Hush…tell you something novel about flash memory

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This slides presents a excellent work on flash memory from Non-Volatile Systems Laboratory, University of California, San Diego.

This slides presents a excellent work on flash memory from Non-Volatile Systems Laboratory, University of California, San Diego.

Published in: Technology, Business

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  • 1. Hush…tell you something novel about flash memory ! Zhichao Liang frankey0207@gmail.com
  • 2. Outline• Background• Some tests• Possible applications• Some extensions
  • 3. Outline• Background• Some tests• Possible applications• Some extensions
  • 4. Background• Flash manufacturers provide conservative and often vague guidelines about performance, energy consumption and reliability.• The lack of detail complicates the design of systems which fully exploit flash memory’s capabilities.
  • 5. Outline• Background• Some tests• Possible applications• Some extensions
  • 6. Test subjectsCharacterizing Flash Memory: Anomalies, Observations, andApplications by Laura M. Grupp, Adrian M. Caulfield, Joel Coburn etc.(MIRCO’09)
  • 7. The testsQuantify known and unknown idiosyncrasies• Performance• Energy Efficiency• Reliability
  • 8. Read Latency• The read latency varies little by manufacturer or chip, and are in good agreement with values from publicly available datasheets.
  • 9. Erase Latency• Erase latency exhibits a smaller gap, but manufacturer B enjoys an advantage for SLC and E for MLC.
  • 10. Program Latency• MLC chips have, on average, longer and enormously variable program latencies.
  • 11. Program Speed Anomaly• Programming speed varies dramatically between pages in MLC devices in a predictable pattern.
  • 12. Performance Increase Anomaly• Performance varies predictably as the devices begin to wear out.
  • 13. Power• The table presents peak power, average power, idle power, and per-operation energy for each operation.
  • 14. Program Energy• Fast and slow pages show a disparity similar to the one we observed for program time.
  • 15. Reliability• Flash memory can corrupt data in three main ways: wear-out, program disturb and read disturb.• 10 erase-program-read cycles + 990 erase- program.• 1 million erases for SLC and 100,000 erases for MLC.
  • 16. Error Rates• The difference between SLC and MLC is stark.
  • 17. Disparity in MLC• MLC chips show large variation in error rates among pages in a single block.
  • 18. Program Disturb• Erase a block and repeatedly program half of one page to 0.
  • 19. Read Disturb• Write a test pattern to several blocks on the flash chip and repeatedly read the pattern back.
  • 20. Summary• Fast pages and slow pages in MLC• High energy-consumption pages and low energy-consumption pages in MLC• Better program performance as wear out for SLC and MLC• High error-rate pages and low error-rate pages in MLC• Program disturb and read disturb
  • 21. Outline• Background• Some tests• Possible applications• Some extensions
  • 22. A variation-aware FTL• Mango adds a priority to incoming IO request and it will do its best to use fast pages for the high-priority writes.• This variation-aware FTL is evaluated in two scenarios: Swap&Netbook.• For Swap, it can significantly increase responsiveness for swap requests.• For Netbook, it can slightly reduce the energy drain on the battery.
  • 23. Flash-aware data encoding• Womcode is a coding techniques makes rewriting wom possible!• Effective lifetime: - SLC: 2*(2/3) = 33% increase - MLC: (2*(2/3) + 1)*(1/2) = 17% increase
  • 24. Outline• Background• Some tests• Possible applications• Some extensions
  • 25. Gordon• A system architecture for data-centric applications that combines low-power processors, flash memory, and data-centric programming.• Performance & Reduced Power ConsumptionGordon: Using Flash Memory to Build Fast, Power-efficient Clusters for Data-intensive Applications by Adrian M. Caufield Laura M. Grupp and Steven Swanson(ASPLOS’09)
  • 26. Gordon Node• 256GB flash storage, a flash storage controller, 2GB of ECC DDR2 SDRAM, a 1.9Ghz Intel Atom processor and other supporting circuitry.
  • 27. Gordon Enclosure• A enclosure holds 16 nodes(4TB storage) and provides 14.4GB/s of aggregate IO bandwidth.
  • 28. Q&A

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