This section tries to point out that the replication is not the same thing as copy-and-migrate. It may seem that the Core simply duplicates objects that have to be replicated and then migrates them to replication clients. The following table lists the biggest (and most obvious) differences between the copy-and-migrate protocol that could be implemented on top of the Core, and the replication:
| copy-and-migrate | replication |
|---|---|
| It's impossible to easily duplicate the whole migration/replication group. | Complete replication groups are replicated. |
| Duplication creates new objects with new object ids. | An object and its replicas have the same object ids. |
| Migration transfers object once. There is no easy way to update the migrated object. | Replication continuously updates replicas until replication request times out, and then destroys them. |
| Migration transfers all properties of the migrated object. | Replication allows you to select which properties should be replicated to a given type of node. Replica updates are very efficient, especially if changes to replicated objects are not frequent, or only some properties of the objects are modified. |