Exadata
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- 2. What is Exadata? “Awonderful blend of hardware and software”. Jonathan Lewis
- 3. How does itlook like? (part 1)
- 4. How does itlook 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 itlook 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!
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- 14. What’s Wrong onNon-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
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- 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 1Cell 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 ● Insteadof 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!
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- 21. Predicate Filtering ● Insteadof 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 1MB1MB 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
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- 24. Do You Wantto 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 4cards x 4 disks x 24GB = 384GB on every storage cell
- 26. Controlling the SFC CELL_FLASH_CACHE NONE DEFAULT KEEP onsegment level DB Developer Friendly Side DBA Admin Ugly Side cellcli on storage level CREATE FLASHCACHE ALTER CELL DROP FLASHCACHE
- 27. DEMO: Smart FlashCache
- 28. HCC: Hybrid ColumnarCompression 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 ● Onlytables 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
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- 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
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- 34. ● Smart filecreation ● 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’tLike ● 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
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