Yup recently been thru that.
Power failure and my 2tb terastation III subsequently set to RAID 0.
Heartbreaking is all i can say.
What I did to get back the data?
Two Words:RAID Recovery.
Check if desktop mainboard got more than 4 sata ports onboard. (Cool I've got 8 sata ports)
Bought a software called UFS Explorer online. (Not cheap but hey data's more impt!)
Installed it then restart computer.
Removed all 4 hdds from my Terastation.
Plug one hdd by hdd into my desktop to make sure it detects all 4 hdds.
Run the UFS explorer program, goto Raid recovery.
Select all 4 hdds with the biggest partitions.
Create soft RAID 5 recovery.
Then did a quick explore and i get to see my data!
Then went out to purchase 4x 2tb hdds WD black series.
Initialized it on my desktop first by plugging it in and seeing it on Disk Management.
Plug it back into the Terastation.
Run tftp-boot as suggested on the top of this main storage forum.
Download and run the firmware update.
After firmware update, create individual share folders in web console.
Map drive folders to computer.
Copy from UFS explorer to individual mapped drives.
There are so many choices so you might want to check out other Raid recovery programs online.