Ceph is designed around the assumption that all components of the system (disks, hosts, networks) can fail, and has traditionally leveraged replication to provide data durability and reliability. The CRUSH placement algorithm is used to allow failure domains to be defined across hosts, racks, rows, or datacenters, depending on the deployment scale and requirements.
Recent releases have added support for erasure coding, which can provide much higher data durability and lower storage overheads. However, in practice erasure codes have different performance characteristics than traditional replication and, under some workloads, come at some expense. At the same time, we have introduced a storage tiering infrastructure and cache pools that allow alternate hardware backends (like high-end flash) to be leveraged for active data sets while cold data are transparently migrated to slower backends. The combination of these two features enables a surprisingly broad range of new applications and deployment configurations.
This talk will cover a few Ceph fundamentals, discuss the new tiering and erasure coding features, and then discuss a variety of ways that the new capabilities can be leveraged.