You are forgetting the time it takes to copy the data to and from these cards. Data may be transported, but it is not usable until you copy it. Copying 20 TiB is probaply going to take some time
Fastest SD card has ~300MB/s read speed and ~250MB/s write speed. Assuming you can write to those cards in parallel, that means you’ll need an additional one hour to write the data to the SD cards and another one hour to read them back. So 4 hours in total which halves the data rates to 1.39 GB/s.
That’s assuming the card can actually sustain ~250MB/s write speed during the full 1TB copy. It probably can if the card is freshly formatted but I haven’t actually tested it myself.
You are forgetting the time it takes to copy the data to and from these cards. Data may be transported, but it is not usable until you copy it. Copying 20 TiB is probaply going to take some time
Fastest SD card has ~300MB/s read speed and ~250MB/s write speed. Assuming you can write to those cards in parallel, that means you’ll need an additional one hour to write the data to the SD cards and another one hour to read them back. So 4 hours in total which halves the data rates to 1.39 GB/s.
That’s assuming the card can actually sustain ~250MB/s write speed during the full 1TB copy. It probably can if the card is freshly formatted but I haven’t actually tested it myself.
That’s still very fast
you have the same problem with downloads though. In the end any download rate exceeding your disc write speed doesnt get you there faster.
ofc. you can write as you download, which makes things faster.