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Level 1

1 points

Can't unmount my External Hard Drive?

Hi guys,

I've been using my Seagate Portable Media 500GB external hard drive for Time Machine on Mountain Lion.

Last week, Time Machine's backup failed, with the message "Unable to complete backup. An error occurred while creating the backup folder."

Using Disk Utility, I verified the disk which asked me to repair it. On trying to repair it, I received the message "Couldn't unmount disk". I received this message also when trying to Erase or Partition the drive and I don't know how to take it further.

The drive is still visible in Finder and I can still access its contents.

I've also tried using a new power cable for the drive and I'm having the same results.

Any advice would be great!

Thanks.

iMac (21.5-inch Mid 2011), OS X Mountain Lion (10.8.2)

Posted on Nov 13, 2012 4:14 AM

Best reply

Joe Gramm

Level 5

6,407 points

Posted on Nov 13, 2012 4:42 AM

When this happens to me I boot into the Recovery HD to repair the disk. Restart the computer and hold the Command+R keys until you see the Apple symbol. Once in Recovery HD, select Disk Utility and Repair the Disk.

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16 replies

May 1, 2014 5:53 AM in response to Joe Gramm

Thanks Joe Gramm. This advice (pasted below) helped me when I was about ready to give up. With a microsoft keyboard, I couldn't figure out how to do an equivalent command-R. but I did go into utility and repair the drive which worked.

Joe Gramm wrote:

When this happens to me I boot into the Recovery HD to repair the disk. Restart the computer and hold the Command+R keys until you see the Apple symbol. Once in Recovery HD, select Disk Utility and Repair the Disk.

Can't unmount my External Hard Drive?