My Passport Disconnects during Time Machine Migration to New iMac

I use a 1tb My Passport Essential as my Time Machine Backup.  I upgraded to from a 2009 iMac to a new 2012 iMac.  I did one final backup of about 600gb on the old machine and disconnected the drive and connected it to the new machine.  During setup and migration the drive would transfer for about 2 hours then disconnect itself.  I wiped the machine, reinstalled OS X and started again.  The same thing happened.  This time the drive stopped being recognized and need to be reinitialized.  I used disk utility and the drive checked out, but I had to do a fresh time machine backup.  10 hours later, I started again.  Same disconnection error after about 2 hours.  I then did a fresh backup to a LaCie Rugged firewire drive that I had.  When the WD failed again, I tried with the Lacie via a Thuderbolt adapter.  This time it worked.

Can anyone explain why this is happening?  Should I not be using a My Passport as a time machine backup drive?  Tech Supprt had no answers.

Thanks

Hello,

Have you check the sleep settings of the drive.

By any chance, did you change any of the settings for the drive with WD Smartware?

Where do I check the sleep settings? Since I was using this on a brand new Mac, I don’t believe I could get into system preferences. Thanks for the help. I never touched smart ware.

Hi again,

If you have the WD Smartware installed on your computer, you will be able to go to the settings of the drive and disable the sleep settings if they are on.

Check on page 39 of the user manual

http://www.wdc.com/wdproducts/library/UM/ENG/4779-705057.pdf