after connecting an external WD drive to Mavericks, the system initialize it with a new “EFI” partition and a new EMPTY “MyBook” partition.
This is what happens to many people with many different configurations (raid, usb, thunderbolt, etc…).
My experience here:
Two days ago i bought 2 brand new WD Green 1TB drives. Connected one to my MacBookPro running Mountain Lion via a USB3 dock from Orico, formatted as Mac Ext Journaled. Than copied the content of two 500GB drives to this 1TB drive. All was ok (and unfortunately i formatted the two 500GB drives after copy).
Yesterday i’ve upgraded from Mountain Lion to Mavericks. Then i connected the (above) drive and the system automatically initialized it to a new EFI partition and a new “MyBook” partition, EMPTY. All automatic, no questions!
No WD software were installed on my mac. I’ve just run some drive firmware upgrades months ago, but nothing marked WD was on Application folder. Searched infos on the net, with no help from Apple or WD.
Then i removeed from /library/extensions the 4 files from WD and connected the other brand new WD Green drive. Same thing: automatically formatted as “MyBook” at first connection.
The “funny” thing is that it’s not a MyBook, it’s just a WD Green drive on a usb3 external dock!
But the same thing happens to people with all kind of WD drives, with or without raid, and with different interfaces.
Still not a word from WD?