Issues cloning Mac Install drive

[Seizure1990]

First off, I have already solved this issue. I came here to share the solution (unless this is something everyone knows already. I'm not very experienced with Macs) as well as to ask a clarification question concerning this whole matter.

So to start, the scenario: I had a MacBook Pro with OS X 10.6 installed. I got a new drive, and wanted to swap it in, so I attached it externally to one of the USB ports, and then used Disk Utility to clone the old drive to the new one.

Now, the issues: Upon taking the new, cloned drive and putting it inside the Mac, I found it would NOT boot. Just show the "?" folder icon. When I took the drive out and attached it to USB, it booted externally just fine, with no problems. Also, oddly, if I booted the old drive externally, and kept the new drive inside on SATA, the new drive would NOT show up as a valid partition. Disk Utility showed me that it supposedly had a 40GB FAT partition, with the rest being empty space, even though the cloned drive was HFS+ and should have taken the drive's entire span.

And now the solution: Simply make sure you clone while the NEW drive is INSIDE the Mac, attached to SATA, while booting the original drive you would like to clone off USB. Once done, simply turn off the Mac, detach the external drive, turn it back on, and voila!

As for my question... also pretty simple.... what the crap? Why does it work that way? Am I missing something? What exactly was going on? I literally wasted 4+ hours cloning and re-cloning before I came upon the solution.

Thanks a lot in advance for any information.

[CPressland]

Sounds like it was partitioned in MBR.

but it makes sense to clone OLD(ext) > NEW(int); as USB Read is higher than Write

[Seizure1990]

Sounds like it was partitioned in MBR.

Mhmm. But aside from switching the drives, I did nothing different, so why would it clone in the MBR format one way, and the GUID another? Especially since the original drive was GUID its self. What reason did the clone operation have to switch to MBR?

Is there some limitation that prevents you from formatting drives as GUID when over USB? That seems really silly, but... can't think of what else is going on.

[CPressland]

Disk Utility won't touch the partition table when you clone a Partition, it'll leave it well alone and 100% of disks come with a MBR Partition Table. So unless you specifically told Disk Utility to change this, it would have continued in MBR mode.

When plugging into an Internal (SATA) port, Disk Utility forces all disks to have a GPT Map.

[Seizure1990]

Disk Utility won't touch the partition table when you clone a Partition, it'll leave it well alone and 100% of disks come with a MBR Partition Table. So unless you specifically told Disk Utility to change this, it would have continued in MBR mode.

When plugging into an Internal (SATA) port, Disk Utility forces all disks to have a GPT Map.

I explicitly formatted the drive as GUID multiple times, before and in between clones, so... I've no idea what's up with that then. Maybe I just did something wrong and left it in MBR after all. The computer is gone and I've no way of verifying and testing this anymore. Oh well.

Good to know that Macs force SATA port drives into the proper boot format though.

Thanks for all the info!

[CPressland]

I'm guessing you tried holding option at the EFI?

[Seizure1990]

I'm guessing you tried holding option at the EFI?

I did try that, yep. The new drive did not show up in the boot menu.