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Sungkyunkwan University Sector Level Mappinng FTL Computer engineering, Sungkyunkwan Univ. Oh Gihwan, Han Gyuhwa, Hong Gyeonghwan Jasmine Open-SSD Project Tutorial 2 - Sector Level Mapping FTL
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Sungkyunkwan University Index Sector Level Mapping Consideration : How to Fill Merge Buffer? Write module for sector level mapping Read module for sector level mapping Experiments Conclusion Reference 2
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Sungkyunkwan University Sector Level Mapping LSNPSN.............. 3 Flash Memory Page Sector Mapping Table Merge Buffer
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Sungkyunkwan University Write module (1/4) LSNPSN 200x80... 210x80... 220x80…..... 1000x80... 1010x80.... 100101.............2122............. 4 Flash Memory Page Merge Buffer Sector Mapping Table
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Sungkyunkwan University Considerations : How to Fill Merge Buffer? Fill one merge buffer in order of incoming 1-Buffer : Just put sectors to merge buffer Multi-copy : Just put sectors, but put sectors with succeeding LBAs at once Distribute sectors to several merge buffers by banks Dynamic : Distribute sectors to merge buffers in order of incoming Static : Distribute sectors to merge buffers, but bank number is fixed by LBA 5
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Sungkyunkwan University Write module (2/4). 21............. 22............. 6 Flash Memory Page Merge Buffer 100............. 101............. Sector Mapping Table LSNPSN 200x80... 210x80... 220x80…..... 1000x80... 1010x80...
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Sungkyunkwan University Write module (3/4).............. 7 Flash Memory Page Merge Buffer 100101.............2122............. Sector Mapping Table LSNPSN 200x80... 210x80... 220x80…..... 1000x80... 1010x80...
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Sungkyunkwan University Write module (4/4).............. 8 100101........2122 Flash Memory Page Merge Buffer Sector Mapping Table LSNPSN 200x00... 210x00… 220x00…..... 1000x00… 1010x00…
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Sungkyunkwan University Read module 9. 100101............. 23........2122 Flash Memory Page Merge Buffer Sector Mapping Table LSNPSN 200x00... 210x00... 220x00…..... 1000x80... 1010x80...
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Sungkyunkwan University Experiments Environment Application : Iometer Transfer size –Random test : 512 Bytes, 1 KB, 2KB, 4KB –Sequential test : 128 KB Target FTL Tutorial Greedy Static Sector mapping Dynamic Sector mapping 1 buffer Sector mapping Multi copy Sector mapping 10
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Sungkyunkwan University Experiments results 11 IOPS
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Sungkyunkwan University Experiments results 12 MB/s
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Sungkyunkwan University Experiments results Random Write Test ( Average of four tests ) Sequential Read/Write Test ( Average of four tests ) 13 x10 x8
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Sungkyunkwan University Experiments results Test Without Map Table Caching ( Average of four tests ) Test with Map Table Caching ( Average of four tests ) 14 x 1/50 ~ 1/20 Cache Miss Rate : about 90% (Random Write)
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Sungkyunkwan University Conclusion Small random write performance of sector mapping is GREAT! Sequential read/write performance of sector mapping is LOW… Shrinking mapping table OVERHEAD is important. 15
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Sungkyunkwan University References DFTL: a flash translation layer employing demand-based selective caching of page-level address mappings / 저자 : Aayush GuptaKim, Bhuvan UrgaonkarYoungjae OpenSSD Project - www.openssd-project.org. The Jasmine OpenSSD Platform: FTL Developer's Guide – http://www.openssd-project.org/ The Jasmine OpenSSD Platform: Technical Reference Manual - http://www.openssd-project.org/ 16
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Sungkyunkwan University Q & A 17
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