Three 1T RE3 WD1002FBYS were failed in Raid5, after disassembly the Raid5, and test individually, the firmware and S.M.R.T information are difference, and the reading performance are obviously difference also, the S.N show all disk are still in WD’s quality guarantee!
I’m sorry to hear that you are having problems with your WD drives. Even though the firmware version might vary, as long as the model number is the same between hard drives, the performance should be the same. Check the link below so you can test your hard drives using our DLG utility.
How to test a drive for problems using Data Lifeguard Diagnostics for Windows