So anyway finally set up my new 1513+ and ready to transfer 4TB of data over from dying 1511+. After much consideration, from windows intermediate copy and paste, to rsync, I settled on using an ftp client from the new server, ftp is always the fastest based on my experience with FTP,NFS,Samba on other NASes.
SO installed ipkg to install lftp. Great thing about lftp is the 'mirror' command. Perfect, just call mirror on the directories you wish and BAM it works on its own. I've been moving some App ISOs, videos and Ebooks. The big stuff all move at 90+MB/s and I'm so surprised that even the small files are moving quickly. This backup job will be done in a jiffy.
Oh yah I decided to write this guide not only to inform about using ftp to run a full backup of your NAS to NAS but I also thought of reminding users to also install screen from ipkg (I think?). These TB scale file transfers will take time and you wouldn't want a disconnection on your SSH client to interrupt the session. So with screen, you can detach from the shell and let it run on its own, come back later and check on progress and eventually kill it when you're done.
So yeah, Synology is AWESOME!