In this chapter, you learned:
The CRUSH algorithm provides a decentralized way for Ceph clients to interact with the Red Hat Ceph Storage cluster, which enables massive scalability.
The CRUSH map contains two main components: a hierarchy of buckets that organize OSDs into a treelike structure where the OSDs are the leaves of the tree, and at least one CRUSH rule that determines how Ceph assigns PGs to OSDs from the CRUSH tree.
Ceph provides various command-line tools to display, tune, modify, and use the CRUSH map.
You can modify the CRUSH algorithm's behavior by using tunables, which disable, enable, or adjust features of the CRUSH algorithm.
The OSD map epoch is the map's revision number and increments whenever a change occurs.
Ceph updates the OSD map every time an OSD joins or leaves the cluster and OSDs keep the map synchronized among themselves.
Click CREATE to build all of the virtual machines needed for the classroom lab environment. This may take several minutes to complete. Once created the environment can then be stopped and restarted to pause your experience.
If you DELETE your lab, you will remove all of the virtual machines in your classroom and lose all of your progress.