HP OpenVMS Systems

Application Performance (I/O) Tuning?

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The Question is:

 
We have a Alpha 1200 5/533, Model 1736.  Is there a document that will help me
 interpret the VMS Monitor Utility statistics as they relate to this Alpha.
 
Example:  If TOTAL DISK I/O is 67/second is this OK on Alpha.  What is the
 maximum DISK I/O Alpha 1200 will support?
 
Thanks,
 
Pat
 

The Answer is :

 
  The OpenVMS Wizard is not aware of information available to the level
  of detail that you seek, as the permutations -- disks and disk spindle
  performance, SCSI controllers, SCSI configuration specifics, contention
  from other hosts on the same SCSI, caching and application I/O patterns,
  etc -- are huge.
 
  Key among disk access specifics here are the disk queue lengths, and not
  the disk queue rates -- disk queue rates above 0.5 indicate that at least
  half of all I/O is waiting.  If the queue lengths climb, the aggregate
  I/O rate is too high.
 
  Also of interest would be I/O caching efficiency, as a correctly tuned
  application will often tend to be CPU-bound, and not I/O bound -- CPU
  and memory (cache) are far faster than physical disk media.  (OpenVMS
  V7.3 and later has XFC support, a wholely new I/O cache design.)
 
  For general performance information, please see the performance manual.
 

  

     

     
answer written or last revised on ( 9-JUL-2001 )
     
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