Intro to Ceph
===============
-Whether you want to provide :term:`Ceph Object Storage` and/or :term:`Ceph Block
-Device` services to :term:`Cloud Platforms`, deploy a :term:`Ceph Filesystem` or
-use Ceph for another purpose, all :term:`Ceph Storage Cluster` deployments begin
-with setting up each :term:`Ceph Node`, your network and the Ceph Storage
-Cluster. A Ceph Storage Cluster requires at least one Ceph Monitor and at least
-two Ceph OSD Daemons. The Ceph Metadata Server is essential when running Ceph
-Filesystem clients.
-
-.. ditaa:: +---------------+ +---------------+ +---------------+
- | OSDs | | Monitor | | MDS |
- +---------------+ +---------------+ +---------------+
-
-- **Ceph OSDs**: A :term:`Ceph OSD Daemon` (Ceph OSD) stores data, handles data
- replication, recovery, backfilling, rebalancing, and provides some monitoring
- information to Ceph Monitors by checking other Ceph OSD Daemons for a
- heartbeat. A Ceph Storage Cluster requires at least two Ceph OSD Daemons to
- achieve an ``active + clean`` state when the cluster makes two copies of your
- data (Ceph makes 3 copies by default, but you can adjust it).
-
-- **Monitors**: A :term:`Ceph Monitor` maintains maps of the cluster state,
- including the monitor map, the OSD map, the Placement Group (PG) map, and the
- CRUSH map. Ceph maintains a history (called an "epoch") of each state change
- in the Ceph Monitors, Ceph OSD Daemons, and PGs.
-
-- **MDSs**: A :term:`Ceph Metadata Server` (MDS) stores metadata on behalf of
- the :term:`Ceph Filesystem` (i.e., Ceph Block Devices and Ceph Object Storage
- do not use MDS). Ceph Metadata Servers make it feasible for POSIX file system
- users to execute basic commands like ``ls``, ``find``, etc. without placing
- an enormous burden on the Ceph Storage Cluster.
-
-Ceph stores a client's data as objects within storage pools. Using the CRUSH
-algorithm, Ceph calculates which placement group should contain the object,
-and further calculates which Ceph OSD Daemon should store the placement group.
-The CRUSH algorithm enables the Ceph Storage Cluster to scale, rebalance, and
-recover dynamically.
-
+Whether you want to provide :term:`Ceph Object Storage` and/or
+:term:`Ceph Block Device` services to :term:`Cloud Platforms`, deploy
+a :term:`Ceph Filesystem` or use Ceph for another purpose, all
+:term:`Ceph Storage Cluster` deployments begin with setting up each
+:term:`Ceph Node`, your network, and the Ceph Storage Cluster. A Ceph
+Storage Cluster requires at least one Ceph Monitor, Ceph Manager, and
+Ceph OSD (Object Storage Daemon). The Ceph Metadata Server is also
+required when running Ceph Filesystem clients.
+
+.. ditaa:: +---------------+ +------------+ +------------+ +---------------+
+ | OSDs | | Monitors | | Managers | | MDSs |
+ +---------------+ +------------+ +------------+ +---------------+
+
+- **Monitors**: A :term:`Ceph Monitor` (``ceph-mon``) maintains maps
+ of the cluster state, including the monitor map, manager map, the
+ OSD map, and the CRUSH map. These maps are critical cluster state
+ required for Ceph daemons to coordinate with each other. Monitors
+ are also responsible for managing authentication between daemons and
+ clients. At least three monitors are normally required for
+ redundancy and high availability.
+
+- **Managers**: A :term:`Ceph Manager` daemon (``ceph-mgr``) is
+ responsible for keeping track of runtime metrics and the current
+ state of the Ceph cluster, including storage utilization, current
+ performance metrics, and system load. The Ceph Manager daemons also
+ host python-based plugins to manage and expose Ceph cluster
+ information, including a web-based `dashboard`_ and `REST API`_. At
+ least two managers are normally required for high availability.
+
+- **Ceph OSDs**: A :term:`Ceph OSD` (object storage daemon,
+ ``ceph-osd``) stores data, handles data replication, recovery,
+ rebalancing, and provides some monitoring information to Ceph
+ Monitors and Managers by checking other Ceph OSD Daemons for a
+ heartbeat. At least 3 Ceph OSDs are normally required for redundancy
+ and high availability.
+
+- **MDSs**: A :term:`Ceph Metadata Server` (MDS, ``ceph-mds``) stores
+ metadata on behalf of the :term:`Ceph Filesystem` (i.e., Ceph Block
+ Devices and Ceph Object Storage do not use MDS). Ceph Metadata
+ Servers allow POSIX file system users to execute basic commands (like
+ ``ls``, ``find``, etc.) without placing an enormous burden on the
+ Ceph Storage Cluster.
+
+Ceph stores data as objects within logical storage pools. Using the
+:term:`CRUSH` algorithm, Ceph calculates which placement group should
+contain the object, and further calculates which Ceph OSD Daemon
+should store the placement group. The CRUSH algorithm enables the
+Ceph Storage Cluster to scale, rebalance, and recover dynamically.
+
+.. _dashboard: ../../mgr/dashboard
+.. _REST API: ../../mgr/restful
.. raw:: html
projects / ceph.git / blobdiff