About partition maps and non-bootable FireWire drives

Feb 02, '06 06:26:00AM

Contributed by: Anonymous

I recently discovered the following while trying to get my Mac Mini to boot from a FireWire drive.

I'm a recent switcher. I took some leftover PC parts I had, and combined them with a Mac Mini to make a pretty decent machine. One of those pieces was a 160GB hard drive originally used in a Windows machine. I popped the drive into a FireWire enclosure and connected it to the Mini. I formatted it as Mac OS X Extended (Journaled), and stored media on it for a while with no problems. When I got tired of my slow internal drive, I decided to run the system entirely from the FireWire drive.

I used Carbon Copy Cloner (CCC) to clone my existing installation to the FireWire drive and rebooted, but I couldn't for the life of me get OS X to boot from the drive! I then formatted a very old hard drive and CCC'ed a clean OS X installation onto it, and it was able to boot. After some sleuthing, I figured out the problem:

To boot from a FireWire drive, the drive's partition map must be in the Apple Partition Map format, not the PC Partition Map format.

This is changeable via the Partition tab when you select the disk in Disk Utility (the disk itself, not just the partition.) When I had originally connected the drive, it allowed me to format it as an OS X partition, but it didn't change the format of the partition map itself. A quick reformat and re-CCC, and I'm booting from the FireWire drive!

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