Considerations for configuring High Availability on Storage Container Manager

Similar to configuring High Availability (HA) for the Ozone Manager (OM), there are various factors that you must consider when configuring HA for the Storage Container Manager (SCM).

SCM HA is supported only on new CDP cluster deployments starting with CDP 7.1.7. You can configure SCM HA when adding Ozone as a service through Cloudera Manager.
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For information about adding and deleting services using Cloudera Manager, see the following:
- Adding a service
- Deleting services
To configure SCM HA, you require at least three nodes as SCM hosts so that one SCM node is the leader and the remaining nodes are the followers. The SCM nodes automatically elect a leader.
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The ozone admin scm roles command lists the leader and follower SCM nodes in an Ozone cluster.
A primordial SCM node generates the cluster ID and distributes it across Ozone Manager and DataNodes in an Ozone cluster. A primordial SCM must be running for other SCMs in SCM HA setup to bootstrap initially. If there is an existing SCM instance running and you want to add a new SCM instance, the primordial node configuration needs to be the existing SCM instance only.
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If the primordial SCM is not chosen correctly, the Ozone cluster can encounter issues from OMs and DNs can crash into SCMs.
You must specify one of the three SCM host names as the primordial node using the ozone.scm.primordial.node.id property. In addition, you must specify the SCM service ID using the ozone.scm.service.id property.
If a primordial SCM node is inaccessible, new SCM nodes cannot join an HA configuration.
After you have configured the HA cluster, ensure that you do not change the SCM Ratis port number (9894).
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For information about the various Ozone ports, see Ports Used by Cloudera Runtime Components.