--- upgrade: - | Cinder now uses the RBD trash functionality to handle some volume deletions. Therefore, deployments must either a) enable scheduled RBD trash purging on the RBD backend or b) enable the Cinder RBD driver's enable_deferred_deletion option to have Cinder purge the RBD trash. This adds the new configuration option 'rbd_concurrent_flatten_operations', which limits how many RBD flattens the driver will run simultaneously. This can be used to prevent flatten operations from consuming too much I/O capacity on the Ceph cluster. It defaults to 3. fixes: - | `Bug #1969643 `_: The RBD driver can now delete volumes with other volumes cloned from it (or its snapshots) in cases where deletion would previously fail. This uses the RBD trash functionality.