6TB drive in Macpro 2008/2010
http://eshop.macsales.com/item/OWC/MPRODBKTLG6/

NB - OWC Hard Drive Sled / Bracket for Mac Pro 2009, 2010-2012 'Westmere' &amp; 'Nehalem' Models ONLY, (not for Mac Pro 2006-2008 Models)


  OWC Hard Drive Bracket
  
  for Mac Pro (2009-2012)  
  
  Updated for 2015, the OWC Hard Drive Bracket is the new universal standard to install any SATA hard drive in a Mac Pro tower, including the latest 6.0TB SATA hard drives which feature the new industry-standard mounting screw pattern. With screw mounting holes for all SATA drives, it's the drive sled built for compatibility, flexibility, and ease of use.
  
  Update your trays or use a spare  
  
  
  Rotate backups
  Separate storage for individual clients or large projects
  Simple, inexpensive way to transfer large files between two Mac Pro models
  Utilize all 3.5" SATA and SAS drives including newer models of 6.0TB and larger capacities utilizing the new screw hole mounting pattern.
  
  
  NOTE: These are compatible with the two standards of drive mounting and the screws are shorter than the stock tray so they are also compatible with drives with shorter screw hole depths, such as the Western Digital RE and RED.


&amp; apologies for the advertising, no afilliation ;-)