5 Replies Latest reply: Apr 9, 2014 12:56 PM by magicat777
Kai Staats Level 1 Level 1 (0 points)

(data for visual reference)

 

USB 1.1 - 12 Mbit/s

USB 2.0 - 480 Mbit/s

USB 3.0 - 5 Gbit/s

 

SATA revision 1.0 - 1.5 Gbit/s - 150 MB/s

SATA revision 2.0 - 3 Gbit/s - 300 MB/s

SATA revision 3.0 - 6 Gbit/s - 600 MB/s

 

When COPYING (not updating) large volumes of data from my internal Segate SATA-III Hybrid drive to an external Seagate USB 3.0 drive, this is what is happening:

 

  • Both using OSX
  • Both data COPY (not updating / integration)
  • rsync (terminal interface) - 50MB/s transfer or 480Mbit/s (exact USB 2.0 speeds)
  • copy (desktop drag-n-drop) - 1GB every 15-18 seconds (again, exact USB 2.0 speeds)

          1GB * 8 = 8Gbit / 15 = 533,333,333 or about 500Mbit/s

          1GB * 8 = 8Gbit / 18 = 444,444,444 or about 444Mbit/s

 

[So, what I have read about rsync -vs- cp is true -- they are identical for fresh copies.]

 

But this means that either Seagate or Apple is lying about supporting USB 3.0. I read a report in Feb 2012 that while Apple claims to support USB 3.0, they have not enabled the driver to force people to upgrade to Thunderbolt adapters. Did this change with the Summer 2012 and new models?

 

The ABOUT THIS MAC profile says my USB 3.0 devices are enabled to transfer up to 5GB/s, but clearly, they are running at EXACTLY USB 2.0 speeds.

Even if the Seagate external drive is just SATA-I, then it should be able to deliver 1.2Gbit/s -- 3x what I am seeing! The fact that the speeds are EXACTLY USB 2.0 tells me the MacBook Pro, while claiming USB 3.0 speeds is nothing more than a USB 2.0 port.

 

Can someone explain what is happening?

 

kai


MacBook Pro, Mac OS X (10.7.5)