Boot iMac from USB drive failing

I have an iMac that's a few years old and lately it's been acting a little flaky (more on that in a separate thread).

I have been doing a bunch of homework on the subject and am at the point where I am trying to protect all of my data and enable recovery if/when something catastrophic happens.

I bought a Seagate 2 TB USB external hard drive. I formatted it with two partitions for Mac, one partition at 300 GB to match my internal hard drive size, and then a large partition. When formatting it, I selected the GUID option so it "should" be able to boot an Intel based Mac.

Using AppleJack (in single user mode, of course), I did a deep clean of my system (something I started doing routinely a couple of months ago). Then, using CCC, I backed up my internal hard drive to the 300 GB partition on the new USB drive. CCC claimed the disk would be 'bootable'.

I shutdown my iMac and start it back up again. At the bong, I hold down the Option key, and shortly am presented with two disks to choose from - my existing internal hard drive, and the newly created partition on the new USB hard drive ... I select the new hard drive.

The apple image shows up, spinning wheel starts up, and after a short while, the fail image replaces the apple image (the circle with the slash in it). I also notice, through the above process, the "on light" on the Seagate drive goes off and on a few times - when the fail image comes up, the light is off.

So --- I am hooped. I can't find anything indicating the Seagate drives can't be used to boot a Mac; but is it the root cause? Or is there some other piece of magic I need to do?

Feel free to point out errors in my above procedure.

Thanks in advance.

Blaine

Bumping once before I give up on y'all. ... any ideas?

This probably does apply to your issue but a close friend of mine has a 24" iMac C2d. He had a Seagate external with FW 400/800 and USB 2.0. With Firewire the drive will not power on. Seagate is using some sort of auto power on, and on some systems people are having issues with the drive powering on when plugged into the Firewire port!

We tried USB and it was fine. I just wonder though if your drive has that auto power on feature my friends does? Is there any power switch on the drive? Maybe it's turning off! Just a wild guess based on what my friends seagate 1.5TB drive did.

My drive has it's own power supply, and it seems to be forever spinning - I can feel the vibration when I pick up the drive. However, the USB cable needs to be connected to the computer in order for the light on the drive to come on.

That is exactly the way my friends Seagate works.

Just keeping you up to date.

I learned the Seagate GoFlex Desk drives have a "sleep" function - and - it can be disabled (How to format your FreeAgent drive in Mac OS 10.5+)

I installed the sleep disable utility. Then I tried to boot my iMac from the new drive ... same results ... no joy.