We had a meeting this morning to discuss the unlimited shares spec [1]
and decided the use case wasn't compelling enough to implement this
feature during Pike. We considered a number of different solutions to
the proposed use case as well as other related use cases not mentioned
in the spec but rejected most of them as unworkable, too complex, or
solving problems nobody cares about.
However we did decide that the use case presented in the spec was worth
solving and that it could be solved using a combination of 2 other
features: per-share-type quotas [2] which is ready for review [3][4] and
share usage tracking.
So far Manila hasn't cared whether shares were empty or full, or what
fraction of the space was consumed. We inherited this behavior from
Cinder where it makes little sense care about the used/free space in a
volume, but one of the things that make shares different from volumes is
that their size is a lot more fluid than volumes'.
Resizing shares is trivial on many (but not all) backends where the
"size" of the share is nothing more than a quota enforced by the storage
controller. A natural effect of this is it makes less sense to bill by
share "size" and more sense to bill by share usage.
We agreed during the meeting that we should focus on the share usage
tracking before we consider unlimited shares because that feature is
sufficient to solve the use case in [1] and it's a prerequisite for
unlimited shares and it has significant value whether we end up
implementing unlimited shares or not.
Zhongjun has volunteered to continue to lead this effort and will split
the spec so we can consider the narrower feature for Pike. We expect
there to be interactions with the ceilometer integration effort [5]
which might make it hard to get both done during Pike but the current
plan is to aim to complete both efforts.
-Ben Swartzlander
[1] https://review.openstack.org/#/c/452097/
[2]
http://specs.openstack.org/openstack/manila-specs/specs/pike/support-quotas-per-share-type.html
[3] https://review.openstack.org/#/c/452158/
[4] https://review.openstack.org/#/c/452159/
[5]
http://specs.openstack.org/openstack/manila-specs/specs/pike/ceilometer-integration.html
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