MyBook Studio II Not Mounting -- Disk Utility Failed -- RAID1 Setup

[kneedrag32]

I have a 2TB MyBook Studio II configured as RAID 1.  It was connected to my Airport Extreme as NAS. 

The drive was working like a champ for a number of months, then it suddenly failed to mount.

I connected the drive with Firewire 800 to my MacBook Pro and it still wouldn't mount, so I tried some diagnostics and here's what I found:

• Disk Utility, First Aid, Verify Disk and Repair Disk all did not work.
  "Error: Disk Utility can't repair this disk. Back up as many files as possible, reformat the disk, and restore your backed-up files."
  
  
• WD Drive Manager 2.2.6 says:
  -- Used Space 0%
  -- Tempurature Condition OK
  -- RAID Status Healthy

Can I assume that only one disk is failing? 

If only one disk is failing, how can I determine which disk and how do I replace it?

Thanks friends.

Jeff

[Wizer]

If you are able to test then there's corruption issues.

Use a recovery software to retrieve the data and reformat and rebuild the RAID