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doc/config-cluster/deploying-ceph-conf.rst <-minor edit. doc/start/get-involved-in-the-ceph-community.rst <-removed $ from command line instruction. doc/start/quick-start.rst <-added additional steps. Signed-off-by: John Wilkins <john.wilkins@dreamhost.com>
182 lines
8.8 KiB
ReStructuredText
182 lines
8.8 KiB
ReStructuredText
==========================
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Ceph Configuration Files
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==========================
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When you start the Ceph service, the initialization process activates a series
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of daemons that run in the background. The hosts in a typical RADOS cluster run
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at least one of three processes or daemons:
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- RADOS (``ceph-osd``)
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- Monitor (``ceph-mon``)
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- Metadata Server (``ceph-mds``)
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Each process or daemon looks for a ``ceph.conf`` file that provides their
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configuration settings. The default ``ceph.conf`` locations in sequential
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order include:
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#. ``$CEPH_CONF`` (*i.e.,* the path following the ``$CEPH_CONF`` environment variable)
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#. ``-c path/path`` (*i.e.,* the ``-c`` command line argument)
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#. ``/etc/ceph/ceph.conf``
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#. ``~/.ceph/config``
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#. ``./ceph.conf`` (*i.e.,* in the current working directory)
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The ``ceph.conf`` file provides the settings for each Ceph daemon. Once you
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have installed the Ceph packages on the OSD Cluster hosts, you need to create
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a ``ceph.conf`` file to configure your OSD cluster.
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Creating ``ceph.conf``
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----------------------
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The ``ceph.conf`` file defines:
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- Cluster Membership
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- Host Names
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- Paths to Hosts
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- Runtime Options
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You can add comments to the ``ceph.conf`` file by preceding comments with
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a semi-colon (;). For example::
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; <--A semi-colon precedes a comment
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; A comment may be anything, and always follows a semi-colon on each line.
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; We recommend that you provide comments in your configuration file(s).
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Configuration File Basics
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~~~~~~~~~~~~~~~~~~~~~~~~~
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The ``ceph.conf`` file configures each instance of the three common processes
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in a RADOS cluster.
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+-----------------+--------------+--------------+-----------------+-------------------------------------------------+
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| Setting Scope | Process | Setting | Instance Naming | Description |
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+=================+==============+==============+=================+=================================================+
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| All Modules | All | ``[global]`` | N/A | Settings affect all instances of all daemons. |
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+-----------------+--------------+--------------+-----------------+-------------------------------------------------+
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| RADOS | ``ceph-osd`` | ``[osd]`` | Numeric | Settings affect RADOS instances only. |
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+-----------------+--------------+--------------+-----------------+-------------------------------------------------+
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| Monitor | ``ceph-mon`` | ``[mon]`` | Alphanumeric | Settings affect monitor instances only. |
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+-----------------+--------------+--------------+-----------------+-------------------------------------------------+
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| Metadata Server | ``ceph-mds`` | ``[mds]`` | Alphanumeric | Settings affect MDS instances only. |
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+-----------------+--------------+--------------+-----------------+-------------------------------------------------+
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Metavariables
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~~~~~~~~~~~~~
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The configuration system supports certain 'metavariables,' which are typically
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used in ``[global]`` or process/daemon settings. If metavariables occur inside
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a configuration value, Ceph expands them into a concrete value--similar to how
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Bash shell expansion works.
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There are a few different metavariables:
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+--------------+----------------------------------------------------------------------------------------------------------+
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| Metavariable | Description |
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+==============+==========================================================================================================+
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| ``$host`` | Expands to the host name of the current daemon. |
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+--------------+----------------------------------------------------------------------------------------------------------+
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| ``$type`` | Expands to one of ``mds``, ``osd``, or ``mon``, depending on the type of the current daemon. |
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+--------------+----------------------------------------------------------------------------------------------------------+
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| ``$id`` | Expands to the daemon identifier. For ``osd.0``, this would be ``0``; for ``mds.a``, it would be ``a``. |
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+--------------+----------------------------------------------------------------------------------------------------------+
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| ``$num`` | Same as ``$id``. |
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+--------------+----------------------------------------------------------------------------------------------------------+
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| ``$name`` | Expands to ``$type.$id``. |
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+--------------+----------------------------------------------------------------------------------------------------------+
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| ``$cluster`` | Expands to the cluster name. Useful when running multiple clusters on the same hardware. |
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+--------------+----------------------------------------------------------------------------------------------------------+
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Global Settings
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~~~~~~~~~~~~~~~
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The Ceph configuration file supports a hierarchy of settings, where child
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settings inherit the settings of the parent. Global settings affect all
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instances of all processes in the cluster. Use the ``[global]`` setting for
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values that are common for all hosts in the cluster. You can override each
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``[global]`` setting by:
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1. Changing the setting in a particular ``[group]``.
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2. Changing the setting in a particular process type (*e.g.,* ``[osd]``, ``[mon]``, ``[mds]`` ).
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3. Changing the setting in a particular process (*e.g.,* ``[osd.1]`` )
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Overriding a global setting affects all child processes, except those that
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you specifically override. For example::
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[global]
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; Enable authentication between hosts within the cluster.
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auth supported = cephx
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Process/Daemon Settings
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~~~~~~~~~~~~~~~~~~~~~~~
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You can specify settings that apply to a particular type of process. When you
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specify settings under ``[osd]``, ``[mon]`` or ``[mds]`` without specifying a
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particular instance, the setting will apply to all OSDs, monitors or metadata
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daemons respectively.
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Instance Settings
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~~~~~~~~~~~~~~~~~
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You may specify settings for particular instances of an daemon. You may specify
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an instance by entering its type, delimited by a period (.) and by the
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instance ID. The instance ID for an OSD is always numeric, but it may be
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alphanumeric for monitors and metadata servers. ::
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[osd.1]
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; settings affect osd.1 only.
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[mon.a1]
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; settings affect mon.a1 only.
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[mds.b2]
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; settings affect mds.b2 only.
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``host`` and ``addr`` Settings
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The `Hardware Recommendations <../../install/hardware-recommendations>`_ section
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provides some hardware guidelines for configuring the cluster. It is possible
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for a single host to run multiple daemons. For example, a single host with
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multiple disks or RAIDs may run one ``ceph-osd`` for each disk or RAID.
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Additionally, a host may run both a ``ceph-mon`` and an ``ceph-osd`` daemon
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on the same host. Ideally, you will have a host for a particular type of
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process. For example, one host may run ``ceph-osd`` daemons, another host
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may run a ``ceph-mds`` daemon, and other hosts may run ``ceph-mon`` daemons.
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Each host has a name identified by the ``host`` setting, and a network location
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(i.e., domain name or IP address) identified by the ``addr`` setting. For example::
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[osd.1]
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host = hostNumber1
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addr = 150.140.130.120
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[osd.2]
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host = hostNumber1
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addr = 150.140.130.120
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Monitor Configuration
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~~~~~~~~~~~~~~~~~~~~~
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Ceph typically deploys with 3 monitors to ensure high availability should a
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monitor instance crash. An odd number of monitors (3) ensures that the Paxos
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algorithm can determine which version of the cluster map is the most accurate.
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.. note:: You may deploy Ceph with a single monitor, but if the instance fails,
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the lack of a monitor may interrupt data service availability.
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Ceph monitors typically listen on port ``6789``. For example::
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[mon.a]
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host = hostNumber1
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addr = 150.140.130.120:6789
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Example Configuration File
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~~~~~~~~~~~~~~~~~~~~~~~~~~
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.. literalinclude:: demo-ceph.conf
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:language: ini
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Configuration File Deployment Options
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-------------------------------------
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The most common way to deploy the ``ceph.conf`` file in a cluster is to have
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all hosts share the same configuration file.
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You may create a ``ceph.conf`` file for each host if you wish, or specify a
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particular ``ceph.conf`` file for a subset of hosts within the cluster. However,
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using per-host ``ceph.conf`` configuration files imposes a maintenance burden as the
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cluster grows. In a typical deployment, an administrator creates a ``ceph.conf`` file
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on the Administration host and then copies that file to each OSD Cluster host.
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The current cluster deployment script, ``mkcephfs``, does not make copies of the
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``ceph.conf``. You must copy the file manually.
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