New iMac 27" and USB3: Something must be wrong here (speed)

Hi folks,

I'm using for a couple of weeks the new imac 27 (basic one), and I bought an ICY BOX IB-120CL-U3 and 2 WD green caviar 3To for backup purposes.

I use superduper software to start the first backup copy. I am very surprise to see these figures below: effective speed below 15MB and "max speed" according to system report being 12MB... Any idea? That's annoying as I was seeking for this USB3 speed.

Here the speed in superduper, from the imac drive to the backup drive:


Here the system report:




(The ICY BOX is meant to be UBS3 compatible and I used the blue cable that was in the package.)

Thanks for your help!

After a second try, the max speed I got was much better, nearly 60 MB/sec, not more but looks fine to me.

True, 5400rpm, their purpose is more for backup uses, but I expected something better than USB 1.1