A novel method  to extend flash memory lifetime  in flash-based DBMS Zhichao Liang(Renmin University of China) [email_addr...
Outline <ul><li>Motivation </li></ul><ul><li>Our work </li></ul><ul><li>Experiment evaluation </li></ul><ul><li>Conclusion...
Outline <ul><li>Motivation </li></ul><ul><li>Our work </li></ul><ul><li>Experiment evaluation </li></ul><ul><li>Conclusion...
SSD Write-lifetime 60GB X 5000 =300TB 40TB (60GB drive) 37TB (80GB drive) Maximum amount of data can be written to SSD Ext...
Original sin <ul><li>Erase before write >>> Out-place update </li></ul><ul><li>Limited erase-program cycles >>> Wear out <...
Free space management <ul><li>To maximize the storage space, free space management methods are employed in DBMS </li></ul>...
The endemic <ul><li>Both space maps and free lists are based on the assumption the in-place update is supported  </li></ul...
Outline <ul><li>Motivation </li></ul><ul><li>Our work </li></ul><ul><li>Experiment evaluation </li></ul><ul><li>Conclusion...
The overview <ul><li>The framework of our method </li></ul>
Append in file and memory  <ul><li>Append Only(AO): we replace the traditional methods used in disk-based DBMS with append...
Write buffer (cont.) <ul><li>For insert and update operation </li></ul>
Write buffer (cont.) <ul><li>The advantages </li></ul><ul><li>- reduces the number of small write </li></ul><ul><li>- redu...
Merge operation <ul><li>Write buffer&AO affect storage in another way </li></ul>
Merge operation (cont.) <ul><li>Obsolete Address Log (OAL) and merge operation are introduced to compact the pages with “h...
Outline <ul><li>Motivation </li></ul><ul><li>Our work </li></ul><ul><li>Experiment evaluation </li></ul><ul><li>Conclusion...
Experiment evaluation <ul><li>Experiment environment: a flash simulator with a plain FTL Algorithm </li></ul><ul><li>Compa...
Experiment evaluation (cont.) <ul><li>Page read I/O </li></ul><ul><li>Page write I/O </li></ul>
Experiment evaluation (cont.) <ul><li>Total latency </li></ul><ul><li>Tendency of ratio </li></ul>
Outline <ul><li>Motivation </li></ul><ul><li>Our work </li></ul><ul><li>Experiment evaluation </li></ul><ul><li>Conclusion...
Conclusion <ul><li>Contributions </li></ul><ul><li>- we analyze and point out the traditional free space management is use...
Q & A
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A novel method to extend flash memory lifetime in flash based dbms

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A novel method to extend flash memory lifetime in flash based dbms

  1. 1. A novel method to extend flash memory lifetime in flash-based DBMS Zhichao Liang(Renmin University of China) [email_address]
  2. 2. Outline <ul><li>Motivation </li></ul><ul><li>Our work </li></ul><ul><li>Experiment evaluation </li></ul><ul><li>Conclusion </li></ul>
  3. 3. Outline <ul><li>Motivation </li></ul><ul><li>Our work </li></ul><ul><li>Experiment evaluation </li></ul><ul><li>Conclusion </li></ul>
  4. 4. SSD Write-lifetime 60GB X 5000 =300TB 40TB (60GB drive) 37TB (80GB drive) Maximum amount of data can be written to SSD Extending SSD Lifetimes with Disk-Based Write Caches by Gokul Soundarajan. FAST 10
  5. 5. Original sin <ul><li>Erase before write >>> Out-place update </li></ul><ul><li>Limited erase-program cycles >>> Wear out </li></ul><ul><li>The abuse of write can be poison for flash </li></ul><ul><li>- small write >>> storage utilization declines </li></ul><ul><li>- random write >>> frequent erase </li></ul>Behave the write pattern !
  6. 6. Free space management <ul><li>To maximize the storage space, free space management methods are employed in DBMS </li></ul><ul><li>The commonly used </li></ul><ul><li>methods are space </li></ul><ul><li>maps and free lists </li></ul>Towards Effective and Efficient Free Space Management by Mark L. McAuliffe. ACM SIGMOD Record
  7. 7. The endemic <ul><li>Both space maps and free lists are based on the assumption the in-place update is supported </li></ul><ul><li>In-place update is impossible on flash, so … </li></ul>
  8. 8. Outline <ul><li>Motivation </li></ul><ul><li>Our work </li></ul><ul><li>Experiment evaluation </li></ul><ul><li>Conclusion </li></ul>
  9. 9. The overview <ul><li>The framework of our method </li></ul>
  10. 10. Append in file and memory <ul><li>Append Only(AO): we replace the traditional methods used in disk-based DBMS with append only </li></ul><ul><li>- no complicated data structures and useless searches </li></ul><ul><li>- the simplest and fastest algorithm </li></ul><ul><li>Write Buffer: write buffer is a stand-alone area in main memory </li></ul><ul><li>- PagesForRelation & RelationForBuffer </li></ul><ul><li>- flushing out until pages are full or a checkpoint occurs </li></ul>
  11. 11. Write buffer (cont.) <ul><li>For insert and update operation </li></ul>
  12. 12. Write buffer (cont.) <ul><li>The advantages </li></ul><ul><li>- reduces the number of small write </li></ul><ul><li>- reduces the amount of data to write and the number of write operation to execute </li></ul><ul><li>- the number of random write declines </li></ul><ul><li>The disadvantages </li></ul><ul><li>- more logging data to read when the system crashes </li></ul><ul><li>- destroy the data distribution </li></ul><ul><li>- delay the erase operation indirectly </li></ul>Clustering and Non-clustering Effects in Flash Memory Databased by Duck-Ho Bae. 20 th DEXA
  13. 13. Merge operation <ul><li>Write buffer&AO affect storage in another way </li></ul>
  14. 14. Merge operation (cont.) <ul><li>Obsolete Address Log (OAL) and merge operation are introduced to compact the pages with “holes” </li></ul>Write buffer PageId Offset Length 2 48 256 17 56 700 2 4012 120 5 569 400 2 345 3000 Page 2 3376 Page 5 400 Page 17 700 (48, 256) valid valid (345, 3000) valid (4012, 120) valid valid valid
  15. 15. Outline <ul><li>Motivation </li></ul><ul><li>Our work </li></ul><ul><li>Experiment evaluation </li></ul><ul><li>Conclusion </li></ul>
  16. 16. Experiment evaluation <ul><li>Experiment environment: a flash simulator with a plain FTL Algorithm </li></ul><ul><li>Comparison: Traditional method(LRU for buffer management) + Our method(LRU for shared memory) </li></ul><ul><li>Test case: four different trace file </li></ul>Tracefile1 R/W=2/8 Tracefile2 R/W=4/6 Tracefile3 R/W=6/4 Tracefile4 R/W=8/2 A Flexible Simulation Environment for Flash-aware Algorithms by Peiquan Jin. CIKM 09
  17. 17. Experiment evaluation (cont.) <ul><li>Page read I/O </li></ul><ul><li>Page write I/O </li></ul>
  18. 18. Experiment evaluation (cont.) <ul><li>Total latency </li></ul><ul><li>Tendency of ratio </li></ul>
  19. 19. Outline <ul><li>Motivation </li></ul><ul><li>Our work </li></ul><ul><li>Experiment evaluation </li></ul><ul><li>Conclusion </li></ul>
  20. 20. Conclusion <ul><li>Contributions </li></ul><ul><li>- we analyze and point out the traditional free space management is useless on flash </li></ul><ul><li>- we propose to use AO & write buffer to reduce the small write and random write </li></ul><ul><li>Future work </li></ul><ul><li>- Implement the method in real system </li></ul><ul><li>- More standard benchmark test </li></ul>
  21. 21. Q & A
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