As the archival transfers via my computer take up so much time, Balt made a setup with a Raspberry Pi to make automatic transfers between the NAS and the archive HD. This small app starts at 10pm UTC and runs till 3am UTC.
It first searches for the oldest video folder, and starts to copy this to the archive HD. (Probably this takes up 3,5 hours). Than the app will look for the oldest audio folder, and it will transfer that one. If there is still some time left (up till 3am), it will start to transfer a second video folder … and it will continue till this folder is completely transferred.
If the Raspberry stops working, just restart it :)
Above setup did not work till now.
Instead, we installed a new, more performant switch and do transfers manually via ethernet cable.
It goes rather fast.