The Newer Technology 8TB (2 x 4TB) Guardian MAXimus Enclosure Q 2-Drive RAID 1 from B&H includes the Newer Technology Guardian MAXimus Enclosure Q 2-Drive RAID 1 two 4TB 3.5" SATA III Internal Hard Drives.
The Guardian MAXimus Enclosure Q 2-Drive RAID 1 from Newer Technology provides up to 3.0TB + 3.0TB of (mirrored) storage capacity* in addition to any two standard matched SATA hard drives. Redundancy is achieved by hardware RAID 1 technology. It also gives "live activity" backup/data redundancy of your critical data with Plug and Play simplicity on any Mac or PC. Working with OS X Leopard's Time Machine feature will help you to keep an up-to-date copy of all of your files and documents.