cinder/releasenotes/notes/bp-provisioning-improvements-bb7e28896e2a2539.yaml

---
features:
  - Cinder now supports the use of 'max_over_subscription_ratio = auto' which
    automatically calculates the value for max_over_subscription_ratio in the
    scheduler.
Overprovisioning Improvements This is part of the effort to improve Cinder's Thin provisioning support. As some operators have been facing problems to determinte what is the best value for the max_over_subscription_ratio, we add in this patch a mechanism to automatically calculate this value. The formula used for calculation is: max_over_subscription_ratio = 20 if provisioned_capacity_gb == 0 else: max_over_subscription_ratio = 1 + (provisioned_capacity_gb/( total_capacity_gb - free_capacity_gb + 1)) Using this formula, the scheduler will allow the creation of a much bigger number of volumes at the begginning of the pool's life, and start to restrict the creation as the free space approaces to 0 or the reserved limit. Drivers now can set max_over_subscription_ratio = 'auto' and take benefit of the change. Drivers that somehow use the max_over_subscription_ratio inside the driver to do any kind of calculations are incompatible with this new feature and should get fixed in order to be able to use the feature. Implements: bp provisioning-improvements Change-Id: If30bb6276f58532c0f78ac268544a8804008770e 2018-01-10 21:14:07 -02:00			`---`
			`features:`
			`- Cinder now supports the use of 'max_over_subscription_ratio = auto' which`
			`automatically calculates the value for max_over_subscription_ratio in the`
			`scheduler.`