HP OpenVMS Systems

Benefits of moving CIXCD to private XMI?

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The Question is:

 
DEC 7000 system with two CIXCDs, each goes to
a separate star coupler.  Will the addition
of a second DWLMA improve I/O bandwidth if
I move one of the CIXCDs to the new DWLMA?
 
Thanks
 
 

The Answer is :

 
  The potential for improvement depends highly on what particular
  factor is constraining the current performance.
 
  Some other things to consider: the overall bandwidth of a CIXCD is
  substantially less than the overall bandwidth of an XMI.  Two CIXCDs
  cannot saturate an XMI.  Whether you'll see any performance benefit
  of splitting the CIXCDs depends on what else is going happening on
  that XMI bus; without this knowledge we cannot make recommendations.
 
  You should consider enabling fast path, if this is a multiprocessor
  system.  This will move a substantial amount of I/O processing off
  the primary processor, relieving the interrupt stack load on the
  primary.  This may not improve I/O bandwidth, but it can improve
  overall system throughput.  (Of course, if the primary processor
  I/O capabilities are not your performance-limiting factor, you may
  not see any improvements.)
 
  That said, there is no substitute for a detailed analysis of system
  performance, particularly with a goal of identifying bottlenecks.
  Simply throwing hardware at the problem without such an analysis
  will probably not solve it, and may make things worse.
 

  

     

     
answer written or last revised on ( 27-APR-1999 )
     
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