OKD 4 contains new technologies and functionality that result in a cluster that is self-managing, flexible, and automated. OKD 4 clusters are deployed and managed very differently from OKD 3.
The most effective way to migrate from OKD 3 to 4 is by using a CI/CD pipeline to automate deployments in an application lifecycle management framework.
If you do not have a CI/CD pipeline or if you are migrating stateful applications, you can use the Migration Toolkit for Containers (MTC) to migrate your application workloads.
To successfully transition to OKD 4, review the following information:
Installation and upgrade
Storage, network, logging, security, and monitoring considerations
File system and snapshot copy methods for persistent volumes (PVs)
Direct volume migration
Direct image migration
Automating your migration with migration hooks
Using the MTC API
Excluding resources from a migration plan
MigrationController custom resource for large-scale migrations
Enabling automatic PV resizing for direct volume migration
Enabling cached Kubernetes clients for improved performance