Updated the RBD driver to include qos functionality.
With Ceph we can define many pools, each pool can use different OSDs (disk/server).
A pool can easily represent a QoS capability.
Example: a pool can use only SSD, a other one can use disk cached on SSD, and a last one use only cheap disk.
Cinder should allow to choice the rbd pool in function of a metadata of the volume during the creation.
Not sure but we should consider whether this is superseded now that we have the pool implementation in Juno. What your'e describing here isn't really QoS but instead Pools implementation to try and distribute work-loads etc.
Regardless, should probably take a turn on the bp to take advantage of the Pools implementation that's already done.
* Blueprints in grey have been implemented.