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 allocation of a virtual disk to a physical storage, it may be useful to allow
the overcommitment of disk space. 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, To enable scheduling instances while overcommitting disk resources on the node,
adjust the value of the ``disk_allocation_ratio`` configuration option to adjust the value of the ``disk_allocation_ratio`` configuration option to
greater than ``1.0``: greater than ``1.0``: