Disk Utility cannot unmount disk, despite booting from a different disk.

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Disk Utility cannot unmount disk, despite booting from a different disk.

I'm running a Mac Pro 12 core with Snow Leopard. I have two start up disks, an SSD and a 4 TB SATA. Upon start up with either disk I can do one or two simple things opening a disk, emptying the trash... small things like this) before I get the BBOD... When I try verifying the 4TB disk, I get a couple of errors, and a notice to repair the disk. When I try to repair the disk, it says the disk cannot be unmounted. I've booted from my SSD, but can't get the 4TB to unmount so I can repair it with Disk Utility.

Any suggestions?

MacBook Pro, iOS 6.1.6, 10.6.8 OS

Posted on Mar 14, 2018 8:29 AM

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Answer 1

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Darvadee Author

Level 1

8 points

Mar 15, 2018 1:22 AM in response to Darvadee

In case anyone else runs into this, I took the Mac Pro startup disk that was causing problems out of the casing, put it in an external reader, plugged it into my MacBook Pro, and repaired it with disk utility on my laptop. Took about 30 seconds, and now works perfectly.

I wish I had thought of that before spending about 30 hours trying to repair it with the Mac Pro.

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Answer 2

Darvadee Author

Level 1

8 points

Mar 14, 2018 2:57 PM in response to Klaus1

I've been running this configuration for several years . . . I recently moved. The first time I used it, no problem - all worked well. I left to go get a load for a couple of weeks. When I got back, I've been completely unable to do ANYTHING .... I've spent hours force quitting by holding down the start button, then trying again. I've booted in Safe Mode - Same Problem.

I've pretty much run out of ideas, but I was thinking if I plugged the disks externally into my laptop, I might be able to repair them from there? I just don't know how to unmount a disk that is not being used as the OS disk. .

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Answer 3

Klaus1

Level 9

52,749 points

Mar 14, 2018 12:33 PM in response to Darvadee

This may, repeat may, be a question of size limitation of a hard drive in older Macs. Or possibly one of formatting.

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Disk Utility cannot unmount disk, despite booting from a different disk.

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