Exadata
- 2. What is Exadata? “A wonderful blend of hardware and software”. Jonathan Lewis
- 3. How does it look like? (part 1)
- 4. How does it look like? (part 2) Source: http://oraclefromguatemala.blogspot.ro/2013/04/lossaboresycoloresdeoracleexadata.html S S S S DB DB DB DB X28 Full Rack
- 5. How does it look like? (part 3) The Exadata rack, available at SCC. Oracle 11.2 3 cell/storage servers 2 DB servers Eth + IB switches + KVM Just a quarter RAC!
- 14. What’s Wrong on Non-Exadata? HDD SAN NAS ORACLE Instance IO Subsystem IO traffic Optimization? 1. Bigger pipe 2. Less IO traffic
- 15. Exadata Architecture – The Big Picture Cell Server 1 Cell Server 2 Cell Server 3 DB Server1 DB Server2 iDB / RDS Oracle Linux Oracle 11.2 ASM Oracle Linux cellsrv DB side Storage side
- 17. DEMO 1 - Magic Switch: ON/OFF 640mil rows Magic OFF Magic ON select count(*) from vanzari where valoare < 100; cell_offload_processing ~10x faster
- 18. Smart Scan Magic DB Node Cell Node 1 Cell Node 2 Cell Node 3 select sum(valoare) from vanzari where tara = ‘RO’; ASM IDB protocol Get blocks from VANZARI Info about the query. Direct path read? Column projection Predicate filtering Storage indexes Filtereddata
- 19. Column Projection ● Instead of returning whole Oracle blocks, the storage layer will pump in just the needed column values. ● The IO traffic is reduced. ● For JOINs, besides columns from the SELECT list, the ones from the join are also transferred. YES, “SELECT *” when just some columns are needed isn’t a good idea on Exadata too!
- 21. Predicate Filtering ● Instead of pushing full Oracle blocks from the storage to the Oracle instance, only those records matching the predicate will be pumped in to the wire. ● The IO traffic is reduced (the filtering is done on the storage side) ● Does work for joins too using bloom filters, but on the storge servers.
- 22. Storage Indexes Explained VANZARI table 1MB 1MB 1MB1MB1MB1MB1MB1MB 1MB 1MB1MB1MB1MB1MB 1MB 1MB 1MB1MB1MB1MB1MB min max min max Storage 1 Storage 2 Storage 3 select count(*) from vanzari where vanzari <= 1000; Perfect for: =, <, >, BETWEEN, <=, >=, IN, IS NULL, IS NOT NULL
- 24. Do You Want to Drop all DB Indexes? Think twice! ● There are many scenarios where SI can’t be used (e.g. get the MIN or MAX for a column) ● SI is a transient in-memory structure. Restart a storage server and you lost all storage indexes on that server ● The decision to create a SI is fully automated and it depends on the workload. ● A SI can’t be used to enforce a PK constraint ● SI are limited to only 8 columns/table ● No integration between SI and CBO ● There’s no such thing as functional SI. ● A SI can’t be used for FK columns to avoid locking issues
- 25. Smart Flash Scan 4 cards x 4 disks x 24GB = 384GB on every storage cell
- 26. Controlling the SFC CELL_FLASH_CACHE NONE DEFAULT KEEP on segment level DB Developer Friendly Side DBA Admin Ugly Side cellcli on storage level CREATE FLASHCACHE ALTER CELL DROP FLASHCACHE
- 27. DEMO: Smart Flash Cache
- 28. HCC: Hybrid Columnar Compression Compression Type Description Expected Ratio QUERY LOW LZA compression algorithm. Low CPU and low compression. 4x QUERY HIGH ZLIB (gzip) compression. 6x ARCHIVE LOW ZLIB (gzip) but with a higher compression level. 7x ARCHIVE HIGH BZIP2 compression. CPU intensive, high compression rate. 12x
- 29. HCC Pitfalls ● Only tables can be compressed. Indexes are not included. ● Exadata inter-operability only. Pay attention when restoring HCC data on a non-exadata machine.. ● Not good for OLTP. ● May consume a lot of CPU (for compression, but for de- compression too). ● It’s not a true columnar model, so wasn’t really designed having the performance idea in mind
- 30. HCC Demo
- 31. IO Resource Manager ● Tight integration with Database Resource Manager ● Provides IO prioritization ● Can be enforced across different databases hosted on the same Exadata machine ● A very important component for consolidated/shared architectures ● In old versions of Exadata, only physical disks were managed by IORM. Flash disks were not handled by IORM. However, this is not true starting with 11.2.3.3.0. ● Workload optimization: low_latency, high_throughput, balanced, auto
- 33. IORM Demo
- 34. ● Smart file creation ● Improved RMAN Incremental Backups ● Improved RMAN restores ● Flash cache compression (from 11.2.3.3.0) ● Automatic HDD scrubbing and repair Other Exadata Goodies
- 35. Things I don’t Like ● The Exadata official documentation was not public accessible. It’s fixed now via a patch: Patch 10386736: Storage Application for the Grid Environment 11.2.3.2.0 for Linux x86-64 - DOCUMENTATION FOR EXADATA 11.2 ● It’s a closed engineered product. However, according to Kevin Closson, Exadata was originally intended to be an open hardware stack. ● The lack of good integration of CBO with Exadata storage (Bug 10248538: OPTIMIZER COST MODEL NOT EXADATA- AWARE) ● Big room for performance instability (storage indexes, flash cache, direct path read etc.) ● The huge price
- 36. Q & A