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166 lines
4.6 KiB
ReStructuredText
166 lines
4.6 KiB
ReStructuredText
===========
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MON Service
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===========
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.. _deploy_additional_monitors:
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Deploy additional monitors
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==========================
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A typical Ceph cluster has three or five monitor daemons spread
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across different hosts. We recommend deploying five
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monitors if there are five or more nodes in your cluster.
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.. _CIDR: https://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing#CIDR_notation
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When Ceph knows what IP subnet the monitors should use it can automatically
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deploy and scale monitors as the cluster grows (or contracts). By default,
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Ceph assumes that other monitors should use the same subnet as the first
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monitor's IP.
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If your Ceph monitors (or the entire cluster) live on a single subnet,
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then by default cephadm automatically adds up to 5 monitors as you add new
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hosts to the cluster. No further steps are necessary.
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* If there is a specific IP subnet that should be used by monitors, you
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can configure that in `CIDR`_ format (e.g., ``10.1.2.0/24``) with:
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.. prompt:: bash #
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ceph config set mon public_network *<mon-cidr-network>*
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For example:
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.. prompt:: bash #
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ceph config set mon public_network 10.1.2.0/24
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Cephadm deploys new monitor daemons only on hosts that have IPs
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configured in the configured subnet.
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* If you want to adjust the default of 5 monitors, run this command:
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.. prompt:: bash #
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ceph orch apply mon *<number-of-monitors>*
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* To deploy monitors on a specific set of hosts, run this command:
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.. prompt:: bash #
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ceph orch apply mon *<host1,host2,host3,...>*
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Be sure to include the first (bootstrap) host in this list.
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* You can control which hosts the monitors run on by making use of
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host labels. To set the ``mon`` label to the appropriate
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hosts, run this command:
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.. prompt:: bash #
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ceph orch host label add *<hostname>* mon
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To view the current hosts and labels, run this command:
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.. prompt:: bash #
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ceph orch host ls
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For example:
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.. prompt:: bash #
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ceph orch host label add host1 mon
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ceph orch host label add host2 mon
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ceph orch host label add host3 mon
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ceph orch host ls
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.. code-block:: bash
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HOST ADDR LABELS STATUS
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host1 mon
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host2 mon
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host3 mon
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host4
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host5
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Tell cephadm to deploy monitors based on the label by running this command:
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.. prompt:: bash #
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ceph orch apply mon label:mon
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* You can explicitly specify the IP address or CIDR network for each monitor
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and control where it is placed. To disable automated monitor deployment, run
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this command:
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.. prompt:: bash #
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ceph orch apply mon --unmanaged
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To deploy each additional monitor:
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.. prompt:: bash #
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ceph orch daemon add mon *<host1:ip-or-network1> [<host1:ip-or-network-2>...]*
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For example, to deploy a second monitor on ``newhost1`` using an IP
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address ``10.1.2.123`` and a third monitor on ``newhost2`` in
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network ``10.1.2.0/24``, run the following commands:
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.. prompt:: bash #
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ceph orch apply mon --unmanaged
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ceph orch daemon add mon newhost1:10.1.2.123
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ceph orch daemon add mon newhost2:10.1.2.0/24
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.. note::
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The **apply** command can be confusing. For this reason, we recommend using
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YAML specifications.
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Each ``ceph orch apply mon`` command supersedes the one before it.
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This means that you must use the proper comma-separated list-based
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syntax when you want to apply monitors to more than one host.
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If you do not use the proper syntax, you will clobber your work
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as you go.
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For example:
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.. prompt:: bash #
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ceph orch apply mon host1
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ceph orch apply mon host2
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ceph orch apply mon host3
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This results in only one host having a monitor applied to it: host 3.
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(The first command creates a monitor on host1. Then the second command
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clobbers the monitor on host1 and creates a monitor on host2. Then the
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third command clobbers the monitor on host2 and creates a monitor on
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host3. In this scenario, at this point, there is a monitor ONLY on
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host3.)
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To make certain that a monitor is applied to each of these three hosts,
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run a command like this:
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.. prompt:: bash #
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ceph orch apply mon "host1,host2,host3"
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There is another way to apply monitors to multiple hosts: a ``yaml`` file
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can be used. Instead of using the "ceph orch apply mon" commands, run a
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command of this form:
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.. prompt:: bash #
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ceph orch apply -i file.yaml
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Here is a sample **file.yaml** file::
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service_type: mon
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placement:
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hosts:
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- host1
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- host2
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- host3
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