HP OpenVMS Systems

Split I/O counts and performance?

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The Question is:

 
We use Robomon which is reporting high split i/o rates and high window turn
rate - what is the significance of these issues and when do they become a
problem - what can be done about them if they are a performance issue
 
 
 

The Answer is :

 
  A split I/O is generally defined as any I/O request that is split
  or segmented into multiple requests to the device driver.  A "split
  I/O" is counted whenever a segmented I/O is performed and a sys$qio
  call to the device driver is not.
 
  Counts alone are not necessarily an indication of a problem, metrics
  such as response time or throughput are generally far more useful.
  If response or throughput is inadequate, then the examination of the
  entire application environment -- split I/Os, the level of internal
  (dis)organization of the files, excessive disk fragmentation, I/O
  bus and disk performance, system memory, etc -- will all be of
  interest.  Constraints in one area of the system environment can
  cause problems in other areas -- such as insufficient available
  physical memory resulting in reduced cache effectiveness which
  produces higher storage I/O rates.
 

  

     

     
answer written or last revised on ( 10-FEB-2000 )
     
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