What were you saying? You were considering optical barcode and modem-style transmission of data if all other transmission modes fail? No way. That is much too slow when you have gigabytes of data to transfer from one device to another. Oops, sorry, but this is just a statement of fact. Just too much data to transfer across such slow links.
But really, if you are willing to tolerate the worst case, you might get a transmission speed of 32 kbits/s, or 4 KB/s. So how long does it take to transfer 32 GB across this link? 97 days. Yeah, that’s awfully long, but if its been decades since the data has been going anywhere, you might be willing to wait for that kind of thing.
Now what about hundreds of terabytes? Seriously, we need a better way than this. Wow, this means that even RS-232 serial port is much too slow of a medium to transfer large amounts of data across. 100 Mbit/s Ethernet? Okay, that’s better. Gigabit Ethernet and USB 3? Still much better.