Open Source Object Storage for Unstructured Data: Ceph on HP ProLiant SL4540 Gen8 Servers

Glossary
• Cold, warm and hot storage—Temperature in data management refers to frequency and performance of data access in
storage. Cold storage is rarely accessed and can be stored on the slowest tier of storage. As the storage ‘heat’ increases,
the bandwidth over time as well as instantaneous (latency, IOPS) performance requirements increase.
• CRUSH— Controlled Replication Under Scalable Hashing. The algorithm Ceph uses to compute object storage locations.
• Epoch—Ceph maintains a history of each state change in the Ceph Monitors, Ceph OSD Daemons and PGs. Each version
of cluster element state is called an “epoch.”
• Failure domain—An area of the solution impacted when a key device or service experiences failure.
• Federated storage—A collection of autonomous storage resources with centralized management that provides rules
about how data is stored, managed and moved through the cluster. Multiple storage systems are combined and
managed as a single storage pool.
• Object storage—A storage model focusing on data objects instead of file systems or disk blocks; objects have key/value
pairs of metadata associated with them to given the data context. Typically accessed by a REST API, designed for massive
scale and using a wide, flat namespace.
• PGs—Placement Group. A grouping of objects on an OSD; pools contain a number of PGs and many PGs can map to an
OSD.
• Pools—logical partitions for storing objects. Pools set ownership/access to objects, the number of object replicas, the
number of placement groups, and the CRUSH rule set to use.
• RADOS—A Reliable, Autonomic Distributed Object Store. This is the core set of storage software which stores the user’s
data in a Ceph Cluster (MON+OSD).
• REST—Representational State Transfer is stateless, cacheable, layered client-server architecture with a uniform
interface. In this cluster, the REST APIs are architected on top of HTTP.