As it is a business grade product, most of the changes are more aimed at capturing the attention of the business users.
For the detail of the release notes go to the release announcement ore Google; GuardianOS_6_5_023-Product_Information_Bulletin-March_2011-r1.pdf
Or try this link;
http://support.overlandstorage.com/j...earchPage=true
I’m not 100% sure support for 3TB is in there yet, the significant point I was making was that for the older units it won’t matter.