If you just recently upgraded your Mac OS to the free Maverick update, you might want to postpone connecting your external Western Digital hard drive to it. A lot of Mavericks users have reported over at various Apple threads about data loss after connecting their WD drive to computers that underwent the Mavericks upgrade.
The main culprit are the WD software that come with the hard drives and Western Digital has issued a warning against its use until a fix or update has been released.
Dear WD Registered Customer,
As a valued WD customer we want to make you aware of new reports of Western Digital and other external HDD products experiencing data loss when updating to Apple’s OS X Mavericks (10.9). WD is urgently investigating these reports and the possible connection to the WD Drive Manager, WD Raid Manager and WD SmartWare software applications. Until the issue is understood and the cause identified, WD strongly urges our customers to uninstall these software applications before updating to OS X Mavericks (10.9), or delay upgrading. If you have already upgraded to Mavericks, WD recommends that you remove these applications and restart your computer.
The WD Drive Manager, WD Raid Manager, and WD SmartWare software applications are not new and have been available from WD for many years, however solely as a precaution WD has removed these applications from our website as we investigate this issue.
So if you’re on Mavericks, make sure no WD software is installed before plugging in your external WD drive.