HP OpenVMS Systems

Cluster DSSI load balancing?

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The Question is:

 
If a VAX 6620 with two KFMSA controllers
(2 DSSI busses each) were connected to an
Alphaserver 800 with four KFPSA controllers
(one DSSI bus each), and the AlphaServer
served its locally-attached storage to the VAX,
would the VAX's disk IO load from the
AlphaServer be spread across all four
DSSI busses?  If the load-sharing capability
is VMS version-specific, what version is needed?
 
 

The Answer is :

 
  All served storage I/O operations will traverse a single DSSI bus.
 
  The VAX "load sharing" balancing algorithm will attempt to pick the
  least heavily loaded DSSI for the served I/O traffic, thus attempting
  to keep the aggregate I/O load balanced across all of the available
  DSSI connections.
 
  The load balancing is achieved by relocating SCS connections.
 
  Non-served (direct access) operations will traverse the appropriate
  DSSI bus -- the DSSI bus on which the target DSSI device resides.
 

  

     

     
answer written or last revised on ( 24-NOV-1998 )
     
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