:_mod-docs-content-type: CONCEPT
[id="ceph-migration-dcn_{context}"]

= {Ceph} migration for Distributed Compute Node deployments

[role="_abstract"]
Distributed Compute Node (DCN) deployments that host {CephCluster} clusters on compute nodes at edge sites have additional {Ceph} migration considerations because multiple {CephCluster} clusters exist across sites. This section applies only to DCN deployments where {Ceph}, {image_service}, and {block_storage} services are deployed on edge compute nodes.

.Supported edge storage topologies

DCN deployments support the following storage topologies at edge sites:

* Hyperconverged Infrastructure (HCI): {Ceph} daemons run on Compute nodes at each edge site.
* {OpenStackPreviousInstaller}-deployed dedicated storage: {Ceph} runs on separate storage nodes deployed by {OpenStackPreviousInstaller}.
* External {Ceph} cluster: Edge sites connect to pre-existing {CephCluster} clusters not managed by {OpenStackPreviousInstaller}.

.Central site {Ceph} migration

For the central site, migrate {Ceph} daemons from the {OpenStackShort} Controller nodes by using the same process as a non-DCN deployment. For more information, see xref:ceph-daemon-cardinality_migrating-ceph[{Ceph} daemon cardinality].

.Edge site {Ceph} migration

For edge sites that use HCI or {OpenStackPreviousInstaller}-deployed dedicated storage, the {Ceph} daemons can continue to run on their current nodes without migration. The Compute nodes or dedicated storage nodes at edge sites are not decommissioned during adoption, so the {Ceph} daemons remain operational.

For edge sites that use external {Ceph} clusters, no migration is required because the {CephCluster} cluster is not managed by {OpenStackPreviousInstaller}.

.{Ceph} backend configuration

Regardless of the edge storage topology, you must create a Kubernetes secret that contains the {Ceph} configuration and keyrings for all clusters in your DCN deployment. For more information about creating the `ceph-conf-files` secret with multiple cluster configurations, see xref:configuring-a-ceph-backend_migrating-databases[Configuring a {Ceph} back end].
