I wanted to pass something along that I've discovered.... I've been using the inexpensive Costco Seagate 1TB drives to send clients footage and backing up on my own drives (Gtech Mini Drives) as a backup for the client. I usually use my Mac Book Pro for this, but the other day I had to upload the client backup to my MACPRO (8core) via my Thunderbolt 2 Promise Raid. All was good until I decided to transfer the files back to one of the Seagate Drives from Costco. I formatted the drive as a Mac OS Extended via Disk Utility, but the files would not transfer. I received the Error -50 message and the transfer would not work. I even tried a very small PDF file with no luck. Reformatted several times.... changes cables....no luck. As a test I hooked up one of my GTECH Mini drives and all the files transferred with no problem. Not sure what's going on here, but thought I would pass it on in case someone else is planning to use these drives to output media from the new MACPRO.
Bill, double check your settings when you partition the drive. I use a number of these with no ill affects. My drives are formatted as ExFAT, though for cross platform compatibility. The only change I make when I repartition them is to set the "Options" for the partition table type to GUID.