openstack
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nova
Code Issues Proposed changes

Explain why disk_available_least can be negative 

This commit adds a paragaph to explain the circumstances in which
disk_available_least will have a negative value, and why this behaviour is
preferred.

Change-Id: Iaa33c35a14a6f0dc8b1d11803a885dce26722e52
This commit is contained in:
Zara 2019-03-28 16:14:29 +00:00
parent 73edcfae7d
commit 3ed1e88bd2
1 changed files with 6 additions and 0 deletions
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6
doc/source/admin/configuration/schedulers.rst
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@ -453,6 +453,12 @@ sparse or copy on write so that each virtual instance does not require a 1:1
allocation of a virtual disk to a physical storage, it may be useful to allow
the overcommitment of disk space.
When disk space is overcommitted, the value of ``disk_available_least`` can
be negative. Rather than rounding up to 0, the original negative value is
reported, as this way a user can see the amount by which they are
overcommitting, and the disk weigher can select a host which is less
overcommitted than another host.
To enable scheduling instances while overcommitting disk resources on the node,
adjust the value of the ``disk_allocation_ratio`` configuration option to
greater than ``1.0``: