I use the two external ports of my Highpoint RR2642 together with a Sharkoon Quickport adapter. It works perfect for read write operations with HDDs which were partitioned in the Mac Pro. Now I partitioned a 250 GB HDD in the Sharkoon (with GUID table) with two partitions and tried to clone the OS X boot drive on it with disk utility. I then transfered the disk into the Mac Pro. The HDD is not recognized any more. It is shown just as Media and unpartitioned. When I put the HDD back into the Sharkoon I can read the disk again. Has anybody an idea what happened there?