Let’s see how Ceph automatically deploys monitors in this article. At Bobcares, with our Server Management Services, we can handle your server-related issues.

How Ceph automatically deploys monitors?

As the cluster expands, Ceph automatically deploys monitor daemons, and as the cluster contracts, Ceph automatically reduces them. The effective setting of the subnet is necessary for the seamless operation of this automated expansion and shrinking.

When we add additional hosts to the cluster, Cephadm automatically installs up to five monitor daemons if the nodes or the entire cluster is situated on a single subnet. On the new hosts, it set up the monitor automatically. The additional hosts are located on the same subnet as the storage cluster’s bootstrapped host.

Cephadm can also grow and deploy monitors to adapt to changes in the storage cluster’s size.

Pre-requisites: Active Red Hat Ceph Storage cluster, Hosts added to the cluster.

Deployment methods

We can use the placement specification in the CLI for the setup process. We need to specify a different number to run a different number of monitors. The Ceph Orchestrator will choose hosts at random and deploy the monitor to them if we do not indicate the hosts to which the monitor should be deployed.

Firstly, we need to log into the Cephadm shell. Then we can use any of the below methods for the process.

1. We use the placement to deploy monitors on hosts. The syntax is as follows:

ceph orch apply mon --placement="HOST_NAME_1 HOST_NAME_2 HOST_NAME_3"

2. We use the placement to deploy a specific number of monitors on specific hosts with labels. Firstly, we must add the labels to the hosts using the below code:

ceph orch host label add HOSTNAME_1 LABEL

Then deploy daemons using the following code:

ceph orch apply mon --placement="HOST_NAME_1:mon HOST_NAME_2:mon HOST_NAME_3:mon"

3. Using placement, we deploy a specific number of monitors on specific hosts. The syntax is as follows:

ceph orch apply mon --placement="NUMBER_OF_DAEMONS HOST_NAME_1 HOST_NAME_2 HOST_NAME_3"

4. We can deploy monitor daemons randomly on the hosts in the storage cluster using the below code:

ceph orch apply mon NUMBER_OF_DAEMONS

Verification

1. We can list the service. For e.g.,

[ceph: root@host01 /]# ceph orch ls

2. We can also list the hosts, daemons, and processes using the below code:

ceph orch ps command line interface--daemon_type=DAEMON_NAME

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Conclusion

The article sums up the methods to create an automatic deployment of Ceph monitors using the command line interface.