openstack/nova
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Merge "Removed scheduler doc costs section"

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Jenkins 2013-08-09 22:59:42 +00:00 committed by Gerrit Code Review
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21
doc/source/devref/filter_scheduler.rst
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@ -12,11 +12,11 @@ Filtering
During its work Filter Scheduler firstly makes dictionary of unfiltered hosts,
then filters them using filter properties and finally chooses hosts for the
requested number of instances (each time it chooses the least costed host and
appends it to the list of selected costs).
requested number of instances (each time it chooses the most weighed host and
appends it to the list of selected hosts).
If it turns up, that it can't find candidates for the next instance, it means
that there are no more appropriate instances locally.
that there are no more appropriate hosts where the instance could be scheduled.
If we speak about `filtering` and `weighting`, their work is quite flexible
in the Filter Scheduler. There are a lot of filtering strategies for the
@ -259,19 +259,10 @@ driver. The standard nova filters and MyFilter are available to the
FilterScheduler. The RamFilter, ComputeFilter, and MyFilter are used by
default when no filters are specified in the request.
Costs and weights
-----------------
Weights
-------
Filter Scheduler uses so-called **weights** and **costs** during its work.
`Costs` are the computed integers, expressing hosts measure of fitness to be
chosen as a result of the request. Of course, costs are computed due to hosts
characteristics compared with characteristics from the request. So trying to
put instance on a not appropriate host (for example, trying to put really
simple and plain instance on a high performance host) would have high cost, and
putting instance on an appropriate host would have low.
So let's find out, how does all this computing work happen.
Filter Scheduler uses so-called **weights** during its work.
The Filter Scheduler weights hosts based on the config option
``scheduler_weight_classes``, this defaults to