CloudEndure replication is a set of two processes:
Initial sync process, which is simply reading the source disks block-by-block and sending it to the replication server. The duration of this operation only depends on the size of the disks and the available uplink bandwidth.
Continuous Data Protection process happens in parallel with the Initial sync process, when every single write operation to the source disk is being immediately (but asynchronously) sent to the target machine and replayed there. Continuous Data Protection will also continue after the initial sync is finished to ensure the replicated disks continue to be in sync with the source.