Cannot boot from external HD

Question

Level 2

201 points

Cannot boot from external HD

I have an external HD which my iMac backups my system daily. I use CCC for that and it has run fine so far. I never had any problem booting from that HD either by using Option/Alt during booting or thru using System Preferences.

Not now anymore. The iMac (late 2013, 27", FusionDrive) refuses to boot from it.

In System Preferences I can see the external HD as a bootable device. However the iMac still uses the internal drive.

When using Option/Alt I only see the internal drive and the restore partition.

I have made a (new) full backup to the external HD and CCC says it "blessed" the HD. But not possible to boot from. Further I did things like resetting Pram, resetting SMC. But does not help.

So next I installed the iMac from scratch (meaning starting the Internet restore and then do a full erase). But still the iMac will not boot from external.

I have connected the external HD to another Mac (Mini) and there it boots flawlessly. So to me there must be a problem with the iMac. But what can I do, this is a serious problem since I now have a backup but this can not fully be used?

Posted on Jul 11, 2014 11:46 AM

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Answer 1

Best reply

dwbrecovery

Level 3

651 points

Jul 11, 2014 11:58 AM in response to Ton Van Hest

Hi Ton,

Try to boot this external HD via a USB2 hub, which is connected to the iMac.

Refer:

How to check which disk am I booted in to?

http://help.bombich.com/discussions/problems/35039-imac-fusion-drive-clone-not-b ootable

Cheers

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Answer 2

Ton Van Hest Author

Level 2

201 points

Jul 11, 2014 12:09 PM in response to dwbrecovery

Will go out tomorrow and buy one. I do not use USB3 hubs since I had problems with USB3 devices unmounting spontaneously. Will report back here.

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Answer 3

tbirdvet

Level 6

13,731 points

Jul 11, 2014 2:15 PM in response to Ton Van Hest

If it won't boot connected directly to USB on the Mac then I would not think a hub will fix the issue

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Answer 4

Ton Van Hest Author

Level 2

201 points

Jul 12, 2014 4:54 AM in response to dwbrecovery

Replaced the USB3 cable by a USB2 but did not help a bit. Still unbootable.

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Answer 5

Jul 12, 2014 5:26 AM in response to Ton Van Hest

THe usb2 hub is connected to a usb3 port on the iMac?

THe external disk is connected to the usb2 hub?

- confirm with System Information that external hdd is connected at USB hi speed, not USB super speed

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Answer 6

Ton Van Hest Author

Level 2

201 points

Jul 12, 2014 6:24 AM in response to dwbrecovery

If connected using a USB2 cable (there is no hub in between) it connects to the "USB 3.0 Hi-Speed-but" if using a USB3 cable it connects to the "USB 3.0 Superspeed-bus".These also are the only 2 busses shown.

Ons the "USB ....Hi-speed bus" it also shows a "BRCM2072 Hun" and to that connected is a Bluetooth USB-hostcontroller and a FaceTime camera.

There is no "USB Hi Speed" mentioned.

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Answer 7

Jul 12, 2014 10:13 PM in response to Ton Van Hest

- The USB2 hub is the main part of the solution. It will connect the the Mac at USB2 speed.

- By connecting to the USB2 hub, the external drive will boot. At USB3 the drive will not boot.

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Answer 8

Ton Van Hest Author

Level 2

201 points

Jul 12, 2014 10:46 PM in response to dwbrecovery

OMG, are you serious?

I already knew that Apple's implementation of USB was very late and very dumb (ports that use 1st device connected to decide between 2 & 3) but now you are telling me that I have to go out and buy and antique USB2 hub only to be able to boot from an external device?

Sorry to say, Apple is getting ******** and I am getting more and more disgust that I ever start using a Mac. Maybe better switch again.

Any knowledge whether they are going to solve this childish problem?

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Answer 9

Jul 12, 2014 11:31 PM in response to Ton Van Hest

- The issue is only if you want to boot from a USB3 external device.

- There are other ports on your machine that you can boot from, refer: Startup Manager: How to select a startup volume

- The ASC is not where Apple make announcements, Refer to their main website.

- Your question / query / feedback should be referred to : https://ssl.apple.com/support/feedback/

- If you find from Apple a resolution, post back. We would like to hear !

Cheers

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Answer 10

Ton Van Hest Author

Level 2

201 points

Jul 12, 2014 11:42 PM in response to dwbrecovery

My iMac (late 2013) only has USB * Thunderbolt. Buying Thunderbolt is (my opinion) unrealistic for a home user. USB3 reaches similar speed at prices a fraction of Thunderbolt. I really find this once again a very bad business practice of Apple which will not make them more friends.

Thanks for your help. You're not the one to blame. |-))

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