I'm facing the issue to develop a system which archives some data, which was available via a web-server some time before (to selected users). Now the question arises on how to securely transport the valuable data from the live / online server to the air-gapped machine (not neccessarily a "true" server, probably without server OS and server HW).
As the data-amounts are rather small (few GB / half-year, one or two DVDs are enough, one large chunk), I thought about burning the data onto DVDs, wiping the encrypted copies from the online-server and re-encrypting the data on the air-gapped machine for long-term storage.
So much for my idea, now the more "formal" requirement:
I need to transport the data with minimal risk of infecting the air-gapped machine.
Obviously USB-sticks or similar are a bad idea and already have been exploited (thanks BadUSB). I thought DVDs (only once-writeable) are the most secure choice as they deny any sort of back-flowing channel from the archive system to the live-system. I may even mandate the use of some scanning on a secondary machine before the data is to be fed in into the archive.
Please also note that the archive system can't be optimized for availability reasons.
With all this background, my question:
Is there any more secure way of transporting data from an online-system to an airgapped-system than to use DVDs (+ scan-after-burn)?