The goal of this process is to upgrade a manatee of any vintage to Manatee v2. It relies on ZFS send/recv to replicate the data, but is limited to a migration between nodes in ONWM.
Upgrading moray to a forward/backward compatible version is a prerequisite of the upgrade. The usual process is to disable one moray node, double-check the stack reconnects correctly, reprovision that node, and then repeat for other moray nodes.
If there is only one moray node deployed, deploying a second using the new image allows you to upgrade the original node as above.