nova/releasenotes/notes/shuffle-best-hosts-447c1703a5d6d140.yaml
Pavlo Shchelokovskyy 3759f105a7 Allow shuffling hosts with the same best weight
This patch adds a new boolean config option
`[filter_scheduler]shuffle_best_same_weighed_hosts` (default False).

Enabling it will improve scheduling for the case when host_subset_size=1
but list of weighed hosts contains many hosts with the same best weight
(quite often the case for ironic nodes).
On the other hand, enabling it will also make VM packing on hypervisors
less dense even when host weighing is completely disabled.

Change-Id: Icee137e15f264da59a1bdc1dc1ecfeaac82b98c6
Closes-Bug: #1711184
2017-09-19 13:51:15 +00:00

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YAML

---
features:
- |
Added a new boolean configuration option
``[filter_scheduler]shuffle_best_same_weighed_hosts`` (default is False).
Enabling it will spread instances between hosts that have the same weight
according to request spec. It is mostly useful when the
``[filter_scheduler]host_subset_size`` option has default value of 1,
but available hosts have the same weight (e.g. ironic nodes using resource
classes). In this case enabling it will decrease the number of
rescheduling events.
On the other hand, enabling it will make packing of VMs on hypervizors
less dence even when host weighing is disabled.