[dnanian]

Wisecracks? Seriously, I wasn't wisecracking. The problem with showing a statistic is that people compare "real world" results - with a mix of different sized files, I/O patterns, disk placement, metadata updates, etc - with "bus speed" results, unproductively. It's intended to help you determine whether, say, a USB drive is running at low-speed (~.1MB/s) vs. a comparison with box specs.

In general, those specs are "ideal" rates. So, with an infinitely fast destination accepting a single stream writing to a blank disk, you get fast speeds (maybe). On top of that, when people then "test" the drive using Finder, they'll tend to grab a big file or two and copy that - which is, again, a different kind of I/O (two large streams).

Finally, remember that the specs for the drive are almost always in mb (megabits) not MB (megabytes) per second - an 8-times larger number.

We're feeding the files to the system as fast as it will accept them. We then have to update the metadata (which involves additional I/O). But we're not CPU bound, and the backup is proceeding very close to whatever the calls have as their maximum rate.