The 4Big is a RAID unit with 4x1TB disks, and configured as RAID5 yields storage of 3TB. It's been reliable for a year or more, and has travelled 5000km with me on my treks.
After purchasing and attempting recovery with Diskwarrior and TechTool Pro, both failed to see the disk. My next step was a disk recovery service that knew about RAID and Mac volumes, and enquiries led to quotes up to $2500. Yikes!
But then I came across R-Studio for Mac, another piece of data recovery software. I downloaded the demo, and hey PRESTO, it could see the disk and all the files, and a recovery test worked fine. So $79 later I'm here recovering from a near disaster. Going to the backups for so much data would have been weeks of effort.