slick looking portable raid box.
http://www.drobo.com...bo-mini/index.php
Thunderbolt, USB 3.0 connections. Uses 4 laptop drives. Optionally uses a mSATA SDD drive for caching. Supports HFS+ for Mac and NTFS for Windows. Can configure for single or dual drive redundancy.
A friend has the 4-bay Drobo and he's quite happy with it. He said he started with just 2 drives and added more as he filled it up. Once fully expanded, just hot swap small disks with large ones to increase capacity. He hasn't had to do that yet.
His Mac sees it at as 16TB drive no matter what the actual capacity is, so when he's increased capacity it was transparent to the Mac.
I'll most likely get the Drobo mini to use with the Mac mini I plan to replace DirecTV with.