Understanding Solid State Disk and the 11gR2 DB flash cache	<br />Guy Harrison<br />Director R&D, Melbourne<br />www.guyha...
Introductions<br />
Agenda<br />Recap of Traditional Disk drive technologies<br />Solid State Disk (SSD) technologies<br />SSD performance<br ...
5MB HDD circa 1956<br />
28MB HDD - 1961<br />1800 RPM<br />
Plus ca Change....<br />
Moore’s law<br />Transistor density doubles every 18 months<br />Exponential growth is observed in most electronic compone...
Disk trends 2001-2009<br />
SSD to the rescue?<br />
Power consumption<br />
Economics of SSD<br />
Hierarchical storage management <br />$/GB<br />$/IOP<br />
Flash Technology concepts<br />Storage Hierarchy:<br />Cell: One (SLC) or Two (MLC) bits<br />Page: Typically 4K <br />Blo...
Flash SSD performance <br />
Flash write mitigation algorithms <br /><ul><li>Garbage collection and “cleaning” maintains free blocks for writes.
“Write Amplification” measures the efficiency of this algorithm</li></ul>“Wear Levelling” ensures that writes are evenly s...
Oracle DB flash cache <br />Introduced in 11GR2 for OEL and Solaris only<br />OEL patch 8974084<br />Secondary cache maint...
Buffer cache architecture<br />Buffer <br />cache<br />Free <br />Buffer <br />Waits<br />Oracle process<br />DBWR<br />Da...
Db Flash Cache Architecture<br />Buffer <br />cache<br />Oracle process<br />Flash cache<br />DBWR<br />Database <br />fil...
Configuration<br />Create filesystem from flash device<br />Apply OEL patch 8974084<br />SetDB_FLASH_CACHE_FILEand DB_FLAS...
Oracle Db flash cache statistics<br />http://guyharrison.squarespace.com/storage/flash_insert_stats.sql<br />
Flash Cache Efficiency<br />http://guyharrison.squarespace.com/storage/flash_time_savings.sql<br />
Flash cache Contents<br />http://guyharrison.squarespace.com/storage/flashContents.sql<br />
Performance:  Read only<br />
Performance: Read/Write<br />
Write complete waits <br />Flash cache architecture avoids ‘free buffer waits’ due to flash IO, but write complete waits c...
Recommendations<br />Consider a hierarchy of storage – memory, flash, disk, tape (don’t wait for SSD “Nirvana”)<br />Use S...
Spotlight <br />
References<br />Guy Harrison blog (guyharrison.net) postings:<br />http://bit.ly/6yKhlh<br />http://bit.ly/6mrX3k<br />htt...
Upcoming SlideShare
Loading in …5
×

Understanding Solid State Disk and the Oracle Database Flash Cache (older version)

6,105 views

Published on

Presentation given at the Victorian Oracle User group.

Published in: Technology
2 Comments
12 Likes
Statistics
Notes
No Downloads
Views
Total views
6,105
On SlideShare
0
From Embeds
0
Number of Embeds
31
Actions
Shares
0
Downloads
49
Comments
2
Likes
12
Embeds 0
No embeds

No notes for slide
  • Apologies, I’m a database type.....Quest is best known for toad, but we also have enterprise monitoring across all levels of the stackIn Melbourne, SQL Navigator + the spotlights. It’s not a complete co-incidence about the star trek theme.
  • The higher logical read rate overwhelms the HDD
  • Understanding Solid State Disk and the Oracle Database Flash Cache (older version)

    1. 1. Understanding Solid State Disk and the 11gR2 DB flash cache <br />Guy Harrison<br />Director R&D, Melbourne<br />www.guyharrison.net <br />
    2. 2. Introductions<br />
    3. 3. Agenda<br />Recap of Traditional Disk drive technologies<br />Solid State Disk (SSD) technologies<br />SSD performance<br />SSD economics<br />Flash SSD Write IO<br />Oracle DB flash cache architecture<br />Performance comparisons<br />
    4. 4. 5MB HDD circa 1956<br />
    5. 5. 28MB HDD - 1961<br />1800 RPM<br />
    6. 6. Plus ca Change....<br />
    7. 7. Moore’s law<br />Transistor density doubles every 18 months<br />Exponential growth is observed in most electronic components:<br />CPU clock speeds<br />RAM<br />Hard Disk Drive storage density <br />But not in mechanical components<br />Service time (Seek latency) – limited by actuator arm speed and disk circumference <br />Throughput (rotational latency) – limited by speed of rotation, circumference and data density<br />
    8. 8. Disk trends 2001-2009<br />
    9. 9. SSD to the rescue?<br />
    10. 10. Power consumption<br />
    11. 11. Economics of SSD<br />
    12. 12. Hierarchical storage management <br />$/GB<br />$/IOP<br />
    13. 13. Flash Technology concepts<br />Storage Hierarchy:<br />Cell: One (SLC) or Two (MLC) bits<br />Page: Typically 4K <br />Block: Typically 128-512K<br />Writes:<br />Read and first write require single page IO<br />Overwriting a page requires an erase & overwrite of the block<br />Wear endurance:<br />100,000 cycles for SLC before failure <br />5,000 – 10,000 cycles for MLC <br />
    14. 14. Flash SSD performance <br />
    15. 15. Flash write mitigation algorithms <br /><ul><li>Garbage collection and “cleaning” maintains free blocks for writes.
    16. 16. “Write Amplification” measures the efficiency of this algorithm</li></ul>“Wear Levelling” ensures that writes are evenly spread across the drive<br />The TRIM API allows OS to invoke cleanup on file delete<br />Some SSD have extra blocks for write optimization <br />You want an SSD with SLC, TRIM (?) and low write amplification<br />
    17. 17. Oracle DB flash cache <br />Introduced in 11GR2 for OEL and Solaris only<br />OEL patch 8974084<br />Secondary cache maintained by the DBWR, but only when idle cycles permit<br />Architecture is tolerant of poor flash write performance<br />
    18. 18. Buffer cache architecture<br />Buffer <br />cache<br />Free <br />Buffer <br />Waits<br />Oracle process<br />DBWR<br />Database <br />files<br />
    19. 19. Db Flash Cache Architecture<br />Buffer <br />cache<br />Oracle process<br />Flash cache<br />DBWR<br />Database <br />files<br />
    20. 20. Configuration<br />Create filesystem from flash device<br />Apply OEL patch 8974084<br />SetDB_FLASH_CACHE_FILEand DB_FLASH_CACHE_SIZE. <br />Consider Filesystemio_options=setall<br />
    21. 21. Oracle Db flash cache statistics<br />http://guyharrison.squarespace.com/storage/flash_insert_stats.sql<br />
    22. 22. Flash Cache Efficiency<br />http://guyharrison.squarespace.com/storage/flash_time_savings.sql<br />
    23. 23. Flash cache Contents<br />http://guyharrison.squarespace.com/storage/flashContents.sql<br />
    24. 24. Performance: Read only<br />
    25. 25. Performance: Read/Write<br />
    26. 26. Write complete waits <br />Flash cache architecture avoids ‘free buffer waits’ due to flash IO, but write complete waits can still occur on hot blocks.<br />Free buffer waits are still likely against the database files, due to high physical read rates created by the flash cache<br />
    27. 27. Recommendations<br />Consider a hierarchy of storage – memory, flash, disk, tape (don’t wait for SSD “Nirvana”)<br />Use SLC flash SSD with low write amplification. <br />Consider flash SSD datafiles for small tablespaces especially read only. <br />Partitioning a large table might allow more frequently accessed data to reside on flash<br />Consider db flash cache to reduce read IO for large tablespaces (OEL/Solaris only). <br />
    28. 28. Spotlight <br />
    29. 29.
    30. 30.
    31. 31. References<br />Guy Harrison blog (guyharrison.net) postings:<br />http://bit.ly/6yKhlh<br />http://bit.ly/6mrX3k<br />http://bit.ly/dmTFYh<br />Kevin Closson:<br />http://kevinclosson.wordpress.com/2009/12/15/pardon-me-where-is-that-flash-cache-part-ii/<br />General articles on SSD:<br />http://www.anandtech.com/storage/showdoc.aspx?i=3631<br />http://en.wikipedia.org/wiki/Flash_memory<br />

    ×