However, in practice the RTRR backups are so painfully slow that it's almost unusable. As an example, the initial backup of one person's folders from TS-410 to TS-119 takes 7.5 hrs to backup only 13GB of data. The average backup speed is approx 900KB/s. But when I do an RSYNC backup the speeds are much higher at approx 5.7MB/s. Both NAS devices have gigabit ethernet connections. These are the settings for the rync job:

So I could use the rsync protocol, but it's a sync, not a backup that retains versions histories. I really want to use rtrr but at these speeds it's not possible. Why is rtrr so slow compared to rsync, and what can I do to speed it up and make it usable?