I was doing some maintenance on my local NAS. I used the command below to effectively move data from one location to another without losing file attributes.
rsync -avzhP --remove-source-files /mnt/das-2T-1/source/ /mnt/das-2T-1/destination/ [--dry-run]You can also temporarily cancel the move and when you start the command again it continues where it stopped.
I also did some internal replication using replication tasks on my TrueNAS device. This creates a snapshot of the data set to replicate to an empty dataset. The destination dataset is overwritten so this option cannot be used to merge datasets. If you want to merge datasets is best to use the rsync option mentioned above.