WD My Book after sleeping not working on iMac

When the Mac wakes after sleeping for an hour or so, the external drive spins up and the partitions are shown in the finder, but they can’t be read/written to and Time Machine backups fail.
How can I fix it? Thanks

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Hi CarlosJG,

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I have same thing with mine. After MAcbook goes to sleep mode drive does not respond, although it is seen, the light is lit, no blinking. does not respond.
I have to pull out the cable to restart. WD doctor utility did not find any issues.


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Read this post, 4TB My Book Unable to access after sleep Mac
It might have something to do with WD software if you have it install in your system.

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I have a 3 tb WD My Book. It’s not accessible after the Mac sleeps. The only way to use it is to restart the computer again.

I have tried 1) firmware update, 2) uninstalling WD software, 3) changing the sleep setting so the drive doesn’t sleep and 4) changing the system preferences so it does not put drives to sleep. I also followed the instructions on this thread. Nothing worked.

In desperation, I bought a Seagate 4 tb, transferred all of the data to it, reformatted the WD, and transferred the data back. The Seagate works flawlessly; the WD is still inaccessible after sleep. It seems from this board and others that this is a fairly common problem. It seems the WD externals are not compatible with Macs. Maybe the new ones are, but I’m not going to take the chances when sure-fire alternatives exist.