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diff --git a/doc/rados/deployment/ceph-deploy-mon.rst b/doc/rados/deployment/ceph-deploy-mon.rst new file mode 100644 index 00000000..bda34fee --- /dev/null +++ b/doc/rados/deployment/ceph-deploy-mon.rst @@ -0,0 +1,56 @@ +===================== + 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 |