CCC or Disk Utility to clone a Mac HD of one new iMac to another, over ThunderBolt, we are getting I/O errors. Even though the clone fails, the destination system does boot and log in, however, the logins take a very very very long time.

Generally speaking a disk I/O error is indicative of a failure and would explain the long boot time. The failure is commonly limited to the disk drive but a faulty connecting cable or logic board failure are also possible.

Use Disk Utility to repair the disk. You will need to boot from another device to repair the disk - since you used Thunderbolt you can use Thunderbolt Target Disk Mode. Stop after Step 2 and invoke Disk Utility from the other Mac.

Describe any errors Disk Utility reports in red.

OK, by that I assume that you used Disk Utility to repair the subject disk and it reported "The volume (name) appears to be OK" in green.

Also verify you followed the instructions here: http://help.bombich.com/kb/usage-scenarios/i-want-to-clone-my-entire-hard-drive- to-a-new-hard-drive-or-a-new-machine

If so, the Thunderbolt connection begins to look suspicious.

Reinstalling OS X subsequent to the "clone" operation may be an acceptable workaround but you should not have had the I/O errors you describe, nor should the login times (subsequent to the initial login, that is) be unacceptably long. It calls into question the integrity of all the information that was transferrred.

I'll try to attract the attention of a CCC expert who will likely provide more competent assistance. You can also try the Bombich support site: http://help.bombich.com

An additional thought:

Are all of these machines the same build/OS version originally? And, I would use CCC to clone to an external hard drive and use that to clone the system onto another machine.

Here is some info from CCC:

http://help.bombich.com/kb/usage-scenarios/i-want-to-clone-my-entire-hard-drive- to-a-new-hard-drive-or-a-new-machine

FWIW, you'll get the best answer by posting your query to http://help.bombich.com/discussions.

Additionally, peruse the hits from a search there for mass AND deployment.

What are the errors?

Glad to hear you got it resolved - I was not sure, but didn't think that cloning directly from one Mac to another would work.

Thanks for the update askWinters.

Over the past few months Apple issued a number of firmware updates that addressed Thunderbolt, but I do not recall what the exact problem was. If the flaw was what you encountered, each Mac would have required the update before attempting the mass deployment you had in mind.

Here you go askWinters

Thunderbolt Firmware Update v1.2

"This update provides stability fixes for Thunderbolt and Target Disk Mode."

It's not at all unusual for a recently produced Mac not to incorporate similarly recent software or firmware updates. In any event the Mac App Store will offer anything applicable under "Updates".

Before you install it be sure to read: Thunderbolt Firmware Update 1.2: Keeps reappearing and Thunderbolt ports and Target Display Mode may not work