1. 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

2. 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

3. Sungkyunkwan University Sector Level Mapping LSNPSN.............. 3 Flash Memory Page Sector Mapping Table Merge Buffer

4. Sungkyunkwan University Write module (1/4) LSNPSN 200x80... 210x80... 220x80…..... 1000x80... 1010x80.... 100101.............2122............. 4 Flash Memory Page Merge Buffer Sector Mapping Table

5. 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

6. 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...

7. Sungkyunkwan University Write module (3/4).............. 7 Flash Memory Page Merge Buffer 100101.............2122............. Sector Mapping Table LSNPSN 200x80... 210x80... 220x80…..... 1000x80... 1010x80...

8. Sungkyunkwan University Write module (4/4).............. 8 100101........2122 Flash Memory Page Merge Buffer Sector Mapping Table LSNPSN 200x00... 210x00… 220x00…..... 1000x00… 1010x00…

9. Sungkyunkwan University Read module 9. 100101............. 23........2122 Flash Memory Page Merge Buffer Sector Mapping Table LSNPSN 200x00... 210x00... 220x00…..... 1000x80... 1010x80...

10. 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

11. Sungkyunkwan University Experiments results 11 IOPS

12. Sungkyunkwan University Experiments results 12 MB/s

13. Sungkyunkwan University Experiments results  Random Write Test ( Average of four tests )  Sequential Read/Write Test ( Average of four tests ) 13 x10 x8

14. 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)

15. 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

16. 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

17. Sungkyunkwan University Q & A 17