:_mod-docs-content-type: ASSEMBLY
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[id="ceph-migration_{context}"]

= Migrating the {Ceph} cluster

:context: migrating-ceph

[role="_abstract"]
In the context of data plane adoption, where the {rhos_prev_long}
({OpenStackShort}) services are redeployed in {rhocp_long}, you migrate a
{OpenStackPreviousInstaller}-deployed {CephCluster} cluster by using a process
called “externalizing” the {CephCluster} cluster.

There are two deployment topologies that include an internal {CephCluster}
cluster:

* {OpenStackShort} includes dedicated {CephCluster} nodes to host object
  storage daemons (OSDs)

* Hyperconverged Infrastructure (HCI), where Compute and Storage services are
  colocated on hyperconverged nodes

In either scenario, there are some {Ceph} processes that are deployed on
{OpenStackShort} Controller nodes: {Ceph} monitors, Ceph Object Gateway (RGW),
Rados Block Device (RBD), Ceph Metadata Server (MDS), Ceph Dashboard, and NFS
Ganesha. To migrate your {CephCluster} cluster, you must decommission the
Controller nodes and move the {Ceph} daemons to a set of target nodes that are
already part of the {CephCluster} cluster.

.Prerequisites

* Complete the tasks in your {rhos_prev_long} {rhos_prev_ver} environment. For more information, see xref:red-hat-ceph-storage-prerequisites_configuring-network[{Ceph} prerequisites].


include::../modules/con_ceph-daemon-cardinality.adoc[leveloffset=+1]

include::assembly_migrating-ceph-monitoring-stack.adoc[leveloffset=+1]

include::../modules/proc_migrating-ceph-mds.adoc[leveloffset=+1]

include::assembly_migrating-ceph-rgw.adoc[leveloffset=+1]

include::assembly_migrating-ceph-rbd.adoc[leveloffset=+1]

include::../modules/proc_migrating-ceph-post.adoc[leveloffset=+1]

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