Another general question for
Sly.... and others, despite these 'theoretical' speeds for these cable standards, a computer's ability to write to these external drives is a much slower process in my experience - e.g. I have a LaCie SSD to which I backup my MBPro's personal folders - both my laptop & the SSD are USB 3.0 - but if I have a few GBs to back-up (do this weekly), the process takes a good 20-30 seconds rather than a second or less - so, there are many other factors involved than just the potential speed of the connection - right? Thanks for comments - Dave
There aren't "many" other factors involved, usually just one -- the speed of the drives to read (in the case of the drive sending information to the backup drive) or write (in the case of the backup being written to) is the only other real possible "bottleneck" when you're talking about fast connection methods.
Your comment about how your "few GB" backup takes "20-30 seconds" rather than one second indicates to me that you're confused about the difference between gigaBITS (the speed connection methods are advertised, such as USB 3.0's theoretical top speed of 5Gb/second) and gigaBYTES. The latter is eight times larger than the former (8bits=1byte), so if you had let's say 5GB (note the capital B for bytes) to backup and connected it to a drive via USB 3.0, instead of taking one or two seconds, it should take eight to 16 seconds (there's some communication and "handshaking" that goes on with connected drives first, which adds a little bit of time but not much).
Then there's the factor of spinning HDs versus SSDs: for the latter, transfer speed will go as fast as USB 3.0 can handle (more on that in a second), whereas spinning drives have to "spin up" to top speed to do a transfer, which can add a bit more time.
Finally, USB 3.0 doesn't even reach 5.0Gb (small b for bits) per second in real world use. As has been typical of USB since forever, your actual speed is anything up to 40 percent less than the theoretical maximum. When you add these factors together, even between two SSD drives, a 5GB transfer between the two machines is going to take longer than eight seconds (but probably not a lot longer in that case). Throw in one more more traditional spinning drives into the mix, and 20-30 seconds sounds about right/a little on the quick side for such a transfer.
FW and FW 800 had an advantage over USB 1.1 and 2.0 in that it was faster AND it had less "overhead" which brought down the maximum speed in real-world use, so a FW800 connector, for example, could get very close to 800Mb per second under good conditions.
Anyway, hope that clears it up a bit. USB 3.0 is very fast and more than good enough for most consumer usage, Thunderbolt seems to have evolved to where FW was headed eventually (and can be used for FW stuff with an adapter) so its currently considered a "pro" level connector. As mentioned elsewhere, USB 3.1 and beyond (4?) and Thunderbolt 3 look like they are going to converge (TB can already "do" USB using an adapter) as far as connectors go, using the new USB-C connector as seen in the Retina MacBook. Eventually, that port will be both a USB-C and TB connector. Nice.
Thunderbolt 3 brings 40Gb/s to USB-C physical connector | MacNN