Oracle从AWR中计算出Exadata效果的方法

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AWR报告中Exadata特有的信息

 

Instance Activity统计(IO相关)

  • cell physical IO interconnect bytes

–DB服务器以及Cell之间交互的IO尺寸

  • cell physical IO bytes eligible for predicate offload

–成为Smart Scan对象的IO尺寸

  • cell physical IO interconnect bytes returned by smart scan

–通过Smart Scan从Cell返回的IO尺寸

  • cell IO uncompressed bytes

–通过cell处理的非压缩数据尺寸

  • cell physical IO bytes saved by storage index

–通过Storage index减少的IO尺寸

  • cell physical IO bytes saved during optimized file creation

–被卸载的数据文件相关处理的IO尺寸

  • cell flash cache read hits

–对于Smart Flash Cache所要求的次数

 

awr_exadata1

 

计算Exadata的效果的方法

 

  • IO减少效果( Cell offload效率)

–着眼于Read IO 计算

–跟是否压缩无关

 

IO减少效果=[ 1 – {(cell physical IO interconnect bytes returned by smart scan)/ (cell IO uncompressed bytes + cell physical IO bytes saved by storage index)} ] * 100

–计算Uncompress状态下的IO尺寸,以及通过storage index减少的IO减少尺寸的总计以及实际中通过smart scan传送到数据库服务器中的IO尺寸的比例。

exadata_io_less

 

  • 通过Storage Index减少Disk IO的效果

–跟是否压缩无关

(cell physical IO bytes saved by storage index / physical read total bytes) * 100

–对于整体的读入尺寸,可以用StorageIndex计算出减少的比例

exadata_storage_index_less_io

  • Flash Cache 命中率

–与是否压缩无关

Flash Cache 命中率=(cell flash cache read hit / physical read total IO requests) * 100

–计算读入要求的Flash Cache命中率

FlashCache命中率

 

  • IO减少效果

–不仅是Read IO ,计算出储存中可以卸载的write IO

–仅在非压缩的情况下可以计算

 

IO减少效果=[{physical read total bytes + (physical write total bytes) * 3 - cell physical IO interconnect bytes}/ {physical read total bytes + (physical write total bytes) * 3 } ] * 100

–将从合计IO尺寸中减去通过Interconnect的IO尺寸的值,作为存储中被卸载减少的IO尺寸来计算

 

※ 因为cell physical IO interconnect bytes 中包含了ASM的mirroring 的写入,所以要以physical write total bytes 三倍值来计算(二重化时为两倍)

※ 压缩时,也出现过比起实际的磁盘IO量,流入到Interconnect中的IO量变多的例子,这时无法应用这里所谈到的方法

exadata_IO减少效果

 

 


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