I have a QNAP TS-239 Pro NAS server, from which I need to copy a large number of files (>2 TB) to a Synology 409 NAS. I could do it with a Windows computer, but would prefer to do it directly from QNAP NAS without having to have a 3rd machine on.
This far, I have tried scp, but apparently there is no built-in scp in Synology. FTP doesn't work out (at least not with the default QNAP ftp client) because the number of files is too large to manually transfer each directory contents, as there is no option to recursivly ftp the directories - and there's also not enough disk space on QNAP to make an archive file to transfer.
What would be the best way to copy a large number of files in several nested subdirectories from a QNAP NAS to a Synology NAS? Both run Busybox Linux.