initial code repo

[stor4nfv.git] / src / ceph / doc / rados / deployment / ceph-deploy-mon.rst

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+=====================
+ Add/Remove Monitors
+=====================
+
+With ``ceph-deploy``, adding and removing monitors is a simple task. You just
+add or remove one or more monitors on the command line with one command. Before
+``ceph-deploy``,  the process of `adding and removing monitors`_ involved
+numerous manual steps. Using ``ceph-deploy`` imposes a restriction:  **you may
+only install one monitor per host.**
+
+.. note:: We do not recommend comingling monitors and OSDs on 
+   the same host.
+
+For high availability, you should run a production Ceph cluster with **AT
+LEAST** three monitors. Ceph uses the Paxos algorithm, which requires a
+consensus among the majority of monitors in a quorum. With Paxos, the monitors
+cannot determine a majority for establishing a quorum with only two monitors. A
+majority of monitors must be counted as such: 1:1, 2:3, 3:4, 3:5, 4:6, etc.
+
+See `Monitor Config Reference`_ for details on configuring monitors.
+
+
+Add a Monitor
+=============
+
+Once you create a cluster and install Ceph packages to the monitor host(s), you
+may deploy the monitor(s) to the monitor host(s). When using ``ceph-deploy``,
+the tool enforces a single monitor per host. ::
+
+       ceph-deploy mon create {host-name [host-name]...}
+
+
+.. note:: Ensure that you add monitors such that they may arrive at a consensus
+   among a majority of monitors, otherwise other steps (like ``ceph-deploy gatherkeys``)
+   will fail.
+
+.. note::  When adding a monitor on a host that was not in hosts initially defined
+   with the ``ceph-deploy new`` command, a ``public network`` statement needs
+   to be added to the ceph.conf file.
+
+Remove a Monitor
+================
+
+If you have a monitor in your cluster that you'd like to remove, you may use 
+the ``destroy`` option. :: 
+
+       ceph-deploy mon destroy {host-name [host-name]...}
+
+
+.. note:: Ensure that if you remove a monitor, the remaining monitors will be 
+   able to establish a consensus. If that is not possible, consider adding a 
+   monitor before removing the monitor you would like to take offline.
+
+
+.. _adding and removing monitors: ../../operations/add-or-rm-mons
+.. _Monitor Config Reference: ../../configuration/mon-config-ref