I've just sat an old computer with fresh Linux Mint and Bitcoin Core installed to sync from scratch. Since its HDD is 250 GB, I had to enable "pruned mode" since the blockchain is currently 367.2 GB.

Having not synced from scratch since 2013, it feels like this will take an eternity.

Why exactly is it so slow? If I were to download 367.2 GB, yeah, it would take some time, but over Bit Torrent, with tons of seeders (as would be the case for something this popular), it would probably max out my hardware, meaning 10 MB/s (100 Mb/s), and then those many GBs don't seem so large anymore.

But I also realize that it's not just about downloading the data, but about verifying it. This, as I understand it, takes a lot of CPU and I/O power (possibly also RAM). Is this what primarily is slowing down a fresh sync, or is the actual "data distribution" part just sub-optimally optimized?

I realize that the answer, whatever it will be, will not help me download it faster, but still, I have to satisfy my curiosity. The progress indicator says "1%" currently.

I vaguely recall people talking about separately downloading the blockchain and then "feeding" it to Bitcoin Core, but that seems like more work than it'll probably be worth with all the presumed hassle it would entail... And it just goes back to my question: why is the downloading of the data not super fast? Or maybe it is? I frankly have no clue what goes on inside my network cables.



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