projects / ceph.git / blame
| Commit | Line | Data |
|---|---|---|
| 7c673cae FG |
1 | ===================== |
| 2 | Add/Remove Monitors | |
| 3 | ===================== | |
| 4 | ||
| 5 | With ``ceph-deploy``, adding and removing monitors is a simple task. You just | |
| 6 | add or remove one or more monitors on the command line with one command. Before | |
| 7 | ``ceph-deploy``, the process of `adding and removing monitors`_ involved | |
| 8 | numerous manual steps. Using ``ceph-deploy`` imposes a restriction: **you may | |
| 9 | only install one monitor per host.** | |
| 10 | ||
| 9f95a23c | 11 | .. note:: We do not recommend commingling monitors and OSDs on |
| 7c673cae FG |
12 | the same host. |
| 13 | ||
| 14 | For high availability, you should run a production Ceph cluster with **AT | |
| 15 | LEAST** three monitors. Ceph uses the Paxos algorithm, which requires a | |
| 16 | consensus among the majority of monitors in a quorum. With Paxos, the monitors | |
| 17 | cannot determine a majority for establishing a quorum with only two monitors. A | |
| 18 | majority of monitors must be counted as such: 1:1, 2:3, 3:4, 3:5, 4:6, etc. | |
| 19 | ||
| 20 | See `Monitor Config Reference`_ for details on configuring monitors. | |
| 21 | ||
| 22 | ||
| 23 | Add a Monitor | |
| 24 | ============= | |
| 25 | ||
| 26 | Once you create a cluster and install Ceph packages to the monitor host(s), you | |
| 27 | may deploy the monitor(s) to the monitor host(s). When using ``ceph-deploy``, | |
| 28 | the tool enforces a single monitor per host. :: | |
| 29 | ||
| 30 | ceph-deploy mon create {host-name [host-name]...} | |
| 31 | ||
| 32 | ||
| 33 | .. note:: Ensure that you add monitors such that they may arrive at a consensus | |
| 34 | among a majority of monitors, otherwise other steps (like ``ceph-deploy gatherkeys``) | |
| 35 | will fail. | |
| 36 | ||
| 37 | .. note:: When adding a monitor on a host that was not in hosts initially defined | |
| 38 | with the ``ceph-deploy new`` command, a ``public network`` statement needs | |
| 39 | to be added to the ceph.conf file. | |
| 40 | ||
| 41 | Remove a Monitor | |
| 42 | ================ | |
| 43 | ||
| 44 | If you have a monitor in your cluster that you'd like to remove, you may use | |
| 45 | the ``destroy`` option. :: | |
| 46 | ||
| 47 | ceph-deploy mon destroy {host-name [host-name]...} | |
| 48 | ||
| 49 | ||
| 50 | .. note:: Ensure that if you remove a monitor, the remaining monitors will be | |
| 51 | able to establish a consensus. If that is not possible, consider adding a | |
| 52 | monitor before removing the monitor you would like to take offline. | |
| 53 | ||
| 54 | ||
| 55 | .. _adding and removing monitors: ../../operations/add-or-rm-mons | |
| 56 | .. _Monitor Config Reference: ../../configuration/mon-config-ref |