I recently experienced the that my external Western Digital My Book hard drive wouldn’t mount the WD Unlocker partition (for encrypted drives) on Mac OS X as it usually does.

Skimming though the console logs, I found a rather disturbing error message that described why the partition couldn’t be mounted:

28/07/2016 20.48.34,000 kernel[0]: disk2s0s2: alignment error.

After doing some googling, it seemed as if the disk was toast: in some forum posts, WD staff suggested that people should get the disk replaced if they experienced such errors. In other threads, it would seem that people suddenly experienced the error after upgrading to OS X 11.something.

Apparently, it all relates to the partition table information somehow being in an inconsistent/erroneous state, and OS X thus not being able to read the disk at all. OK, so OS X not being able to read the data, let alone not being able to fix the problems, is bad enough by itself, but the thought of not being able to recover the data on the disk at all was pretty annoying.

Luckily, I have had great experiences with installing file system drivers for various non-native file systems in different operating systems, and I thought that installing a driver for OS X’s HFS+ on a Windows box, and attaching the external hard drive to it, just might do the trick, as the driver, and the way that the operating system would access the disk might be different from what OS X does natively.

So, I installed the HFS+ driver for Windows 10 from Paragon Software, and after connecting and unlocking the drive with the Windows-based WD software, the HFS+ partitions showed up, and I was able to access the data without any problems whatsoever. Afterwards I tried reconnecting it to OS X, and the WD Unlocker partition showed up just as it had before the error.