Revision 8a96e60d doc/design-partitioned.rst

b/doc/design-partitioned.rst
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There is already a concept of spindles in Ganeti. It's not related to
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any actual spindle or volume count, but it's used in ``spindle_use`` to
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measure the pressure of an instance on the storage system and in
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``spindle_ratio`` to balance the I/O load on the nodes. These two
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parameters will be renamed to ``storage_io_use`` and
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``storage_io_ratio`` to reflect better their meaning. When
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``exclusive_storage`` is enabled, such parameters are ignored, as
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balancing the use of storage I/O is already addressed by the exclusive
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assignment of PVs.
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``spindle_ratio`` to balance the I/O load on the nodes. When
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``exclusive_storage`` is enabled, these parameters as currently defined
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won't make any sense, so their meaning will be changed in this way:
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- ``spindle_use`` refers to the resource, hence to the actual spindles


  		





  
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  (PVs in LVM), used by an instance. The values specified in the instance


  		





  
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  policy specifications are compared to the run-time numbers of spindle


  		





  
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  used by an instance. The ``spindle_use`` back-end parameter will be


  		





  
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  ignored.


  		





  
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- ``spindle_ratio`` in instance policies and ``spindle_count`` in node


  		





  
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  parameters are ignored, as the exclusive assignment of PVs already


  		





  
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  implies a value of 1.0 for the first, and the second is replaced by


  		





  
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  the actual number of spindles.


  		





  
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When ``exclusive_storage`` is disabled, the existing spindle parameters


  		





  
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behave as before.


  		





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Dedicated CPUs


  		





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