Created on: February 25, 2016
Last updated: June 15, 2017
Some of our 5TB enclosures including one variant of the Mercury Elite Pro (OWCME3QH7T5.0) ship with Toshiba hard drive model MD04ACA500. If you are using a USB-enabled enclosure with this Toshiba drive installed, and you connect the enclosure to the USB 3.0 port on a Late 2013 Mac Pro (MacPro6,1) running OS X 10.9.5, you are likely to encounter performance problems. Transfer rates will be sluggish and in some cases the transfer will stop entirely or "hang". There appears to be an incompatibility between this specific 5TB Toshiba drive and 10.9.5.
While Apple does not have a fix for 10.9.5, there is some evidence that the best way to resolve this issue is to update to OS X 10.10 or later. Once that is done, some customers have reported that the data transfer issues stop, allowing the Toshiba drive to perform normally.