USB and Ethernet, which is more CPU intensive?

Question

When I connect 2 PCs with each other through a 1GigE crossover cable and transfer large files (often larger than 1GB) through FTP, I often got transfer speed of around 70MB/s, which is likely limited by the hard drives and not by Ethernet's bandwidth.

I don't have a USB 3.0 device at hand, but we can safely assume that the limiting factor is still the hard drive's spinning speed (we aren't talking about SSDs here).

So, ceteris paribus, which protocol taxes the processor more (given the same transfer rate ?)

Answer 1

While ultimately the computer's CPU is involved in the process, the reality is that it is so negligible, that it is irrelevant. Both USB and Ethernet have their own controller chips and do not rely on the CPU for instructions or processing power.

Answer 2

Over Gigabit ethernet the max you could ever get is 128MB/s, take into the fact of TCP error checking and the OS having to deal with the file move then you can sat that 70MB per second is about right not every bit sent over the network is the file itself there are a lot more mechanisms in place, Im guessing since your already getting over 66 that your on Sata 1 disks at least. So your bottleneck isn't your hard-drive.

Hard disks

ATA 33 = 33 MB/s

ATA 66 = 66 MB/s

Sata 1 = 187.5 MB/s

Sata 2 = 375 MB/s

Sata 3 = 750 MB/s

Your final question is a bit off topic of your opening but there both cpu un-intensive as there IO devices

Answer 3

Your harddrive is the limiting factor here at 70MB/s. Past the 100 MB/s range, other factors come into heavy play. How do you transfer the files? On the network, FTP is typically the fastest compared to SMB. For SMB, SMB 2.0 will knock the socks off earlier implementations. On the Windows side, that means you'll need Vista SP1/Server 2008 and above. On the Samba side, I don't know of any distros that use SMB 2.

Since there has been little benchmarking information on USB 3, I'll reserve judgement on which will be faster outside the 100MB/s range.