Q I was trying to back up a 60 GB Music folder from one Mac to another, but discovered that the estimated time over Gigabit Ethernet was around 24 hours. How can I make that quicker? Would an external drive be better, or direct to an internal SATA disk?
A By far the fastest transfer for such a large backup would be between two internal SATA drives, for example in the internal bays of an old Mac Pro, which should take a couple of hours or less.
If you have a high-performance SD card of 64 GB capacity, that would be next, although some cards can prove surprisingly slow at times; remember that SD cards are formatted in MS-DOS FAT format, not regular Mac HFS+, though.
After those, transfer over Thunderbolt, USB3, FireWire 800, USB2, or FireWire 400 (in that order of preference) to an external hard disk would take rather longer.
Ethernet, even Gigabit standard, can be significantly slower, although the time quoted to you seems to have been based on 100 Mbps connection rather than 1000 Mbps (which is Gigabit). It would be worth checking your Ethernet cabling to discover why its performance was so slow in this case.
Updated from the original, which was first published in MacUser volume 27 issue 10, 2011.