Ceph Glossary

    Sometimes more than one term applies to a definition. Generally, the firstterm reflects a term consistent with Ceph’s marketing, and secondary termsreflect either technical terms or legacy ways of referring to Ceph systems.

    • Ceph Project

    • The aggregate term for the people, software, mission and infrastructureof Ceph.

    • cephx

    • The Ceph authentication protocol. Cephx operates like Kerberos, but ithas no single point of failure.

    • Ceph

    • Ceph Platform

    • All Ceph software, which includes any piece of code hosted at.

    • Ceph System

    • Ceph Stack

    • A collection of two or more components of Ceph.

    • Ceph Node

    • Node
    • Host

    • Any single machine or server in a Ceph System.

    • Ceph Storage Cluster

    • Ceph Object Store
    • RADOS
    • RADOS Cluster
    • Reliable Autonomic Distributed Object Store

    • The core set of storage software which stores the user’s data (MON+OSD).

    • Ceph Cluster Map

    • Cluster Map

    • The set of maps comprising the monitor map, OSD map, PG map, MDS map andCRUSH map. See Cluster Map for details.

    • Ceph Object Storage

    • The object storage “product”, service or capabilities, which consistsessentially of a Ceph Storage Cluster and a Ceph Object Gateway.

    • Ceph Object Gateway

    • RADOS Gateway
    • RGW

    • The S3/Swift gateway component of Ceph.

    • Ceph Block Device

    • RBD

    • The block storage component of Ceph.

    • Ceph Block Storage

    • The block storage “product,” service or capabilities when used inconjunction with , a hypervisor such as QEMU or Xen, and ahypervisor abstraction layer such as libvirt.

    • CephFS
    • Ceph FS

    • The POSIX filesystem components of Ceph. Refer and Ceph File System formore details.

    • Cloud Stacks

    • Third party cloud provisioning platforms such as OpenStack, CloudStack,OpenNebula, ProxMox, etc.

    • Object Storage Device

    • OSD

    • A physical or logical storage unit (e.g., LUN).Sometimes, Ceph users use theterm “OSD” to refer to , though theproper term is “Ceph OSD”.

    • Ceph OSD Daemon

    • Ceph OSD Daemons
    • Ceph OSD

    • The Ceph OSD software, which interacts with a logicaldisk (OSD). Sometimes, Ceph users use theterm “OSD” to refer to “Ceph OSD Daemon”, though theproper term is “Ceph OSD”.

    • OSD id

    • The integer that defines an OSD. It is generated by the monitors as partof the creation of a new OSD.

    • OSD fsid

    • This is a unique identifier used to further improve the uniqueness of anOSD and it is found in the OSD path in a file called osd_fsid. This term is used interchangeably with uuid

    • OSD uuid

    • Just like the OSD fsid, this is the OSD unique identifier and is usedinterchangeably with fsid

    • bluestore

    • OSD BlueStore is a new back end for OSD daemons (kraken and newerversions). Unlike it stores objects directly on theCeph block devices without any file system interface.

    • filestore

    • A back end for OSD daemons, where a Journal is needed and files arewritten to the filesystem.

    • Ceph Monitor

    • MON

    • The Ceph monitor software.

    • Ceph Manager

    • MGR

    • The Ceph manager software, which collects all the state from the wholecluster in one place.

    • Ceph Manager Dashboard

    • Ceph Dashboard
    • Dashboard Module
    • Dashboard Plugin
    • Dashboard

    • Ceph Metadata Server

    • MDS

    • The Ceph metadata software.

    • Ceph Clients

    • Ceph Client

    • Ceph Kernel Modules

    • The collection of kernel modules which can be used to interact with theCeph System (e.g., , rbd.ko).

    • Ceph Client Libraries

    • The collection of libraries that can be used to interact with componentsof the Ceph System.

    • Ceph Release

    • Any distinct numbered version of Ceph.

    • Ceph Point Release

    • Any ad-hoc release that includes only bug or security fixes.

    • Ceph Interim Release

    • Versions of Ceph that have not yet been put through quality assurancetesting, but may contain new features.

    • Ceph Release Candidate

    • A major version of Ceph that has undergone initial quality assurancetesting and is ready for beta testers.

    • Ceph Stable Release

    • A major version of Ceph where all features from the preceding interimreleases have been put through quality assurance testing successfully.

    • Ceph Test Framework

    • Teuthology

    • The collection of software that performs scripted tests on Ceph.

    • CRUSH

    • Controlled Replication Under Scalable Hashing. It is the algorithmCeph uses to compute object storage locations.

    • CRUSH rule

    • The CRUSH data placement rule that applies to a particular pool(s).

    • Pool

    • Pools

    • Pools are logical partitions for storing objects.

    • systemd oneshot

    • A systemd type where a command is defined in which willexit upon completion (it is not intended to daemonize)

    • Extensible metadata for LVM volumes and groups. It is used to storeCeph-specific information about devices and its relationship withOSDs.