Exploring Ceph cache pool implementation

Sage Weil and Greg Farnum presentation during the Firefly Ceph Developer Summit in 2013 is used as an introduction to the cache pool that is being implemented for the upcoming Firefly release.
The CEPH_OSD_OP_COPY_FROM etc.. rados operations have been introduced in Emperor and tested by ceph_test_rados which is used by teuthology for integration tests by doing COPY_FROM and COPY_GET at random.
After a cache pool has been defined using the osd tier commands, objects can be promoted to the cache pool ( see the corresponding test case ).
The HitSets keep track of which object have been read or written ( using bloom filters ).