VMware vSAN 8.x
VMware vSAN 9.x
Direct migration from vSAN OSA to ESA is not possible because OSA and ESA use fundamentally different on-disk formats and data paths, The migration process requires building a new cluster (or redeploying existing hosts) and migrating data over.
Since an "in-place" upgrade is not possible, the migration must be executed as a Side-by-Side Migration:
Deploy New Cluster: Build a new vSAN ESA cluster using certified hardware.
Create a vSAN Cluster
Cross-Cluster Migration: Use Storage vMotion to move virtual machines from the OSA cluster to the ESA cluster.
Decommission: Once all workloads are migrated and verified, decommission the original OSA cluster.
Note: To incorporate hosts from the Original Storage Architecture (OSA) cluster into the vSAN Express Storage Architecture (ESA) cluster, the existing storage devices must be completely wiped of any previous partitions or metadata. Unlike the Original Storage Architecture (OSA), which uses disk groups, ESA requires disks to be in a "Clean" or "Unmounted" state so they can be claimed by the vSAN ESA Storage Pool
The transition from vSAN Original Storage Architecture (OSA) to Express Storage Architecture (ESA) requires a destructive re-initialization of the storage layer. To execute this :
VM Evacuation: All Virtual Machines must be migrated to a different cluster and datastore via vMotion. If the VMs are not moved the VM's data will be lost.
Maintenance Mode: Place the host in Maintenance Mode.
Select "No Data Migration" (Since all VMs have been moved to different/new cluster and storage).
Decommission and Reformat: Once in Maintenance Mode, the existing OSA Disk Groups must be deleted. The host can then be moved to the data center level in vCenter inventory, post which it can be moved to the ESA-enabled cluster, where the disks can be claimed under the new ESA storage pool format.