From fc3369c5e63588ee411d044fc9f75862b04000ac Mon Sep 17 00:00:00 2001 From: Sage Weil Date: Fri, 7 Jul 2017 15:41:43 -0400 Subject: [PATCH] doc/start/intro: updates Signed-off-by: Sage Weil --- doc/start/intro.rst | 87 ++++++++++++++++++++++++++------------------- 1 file changed, 51 insertions(+), 36 deletions(-) diff --git a/doc/start/intro.rst b/doc/start/intro.rst index 688a6c51495..a416a45ba77 100644 --- a/doc/start/intro.rst +++ b/doc/start/intro.rst @@ -2,42 +2,57 @@ 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 -- 2.39.5