bootable USB 3 external drive for new iMac

You are best in making a HD boot clone, very good idea, ....unless someone jumps into to correct me on same, Mavericks current build is not externally bootable on your newest Mac.

This was an occurrence with the newest Macbook Air for a few months until a new ML build came out. However I will not speculate if or when in this instance of yours.

USB 3 or 2 should have nothing to do with this.

If superduper verified your clone and the HD itself is fine, you can trust same, but as for being externally bootable, that may very have to wait until a Mavericks build change, however when that is...........

There is a bug in the USB 3 specs where you can't boot from one. Not sure if it is just the newer Mac computers with USB 3 or it is on both Mac and Windows style computers. I don't have any Windows PCs and no Mac with USB 3.

But it a widely reported problem. Thunderbolt drive work.

Dale Garrison wrote:

The apparent lack of bootability with USB 3 drives

That is false.

Macs boot from USB fine. I used an SSD drive in a USB3 case to boot up so I could remove the fusion drive gimmick from my iMac, worked perfect.

Worst case, use a flash drive or SD card.

Almost every new OS, from Panther to Tiger to Snow Leopard and Leopard has caused troubles for some users and some external drive enclosures, such as the issue now with WD's enclosure and their software.

Back in SL 10.6.0 some could no longer use Firewire but USB worked, or the reverse.

In fact how you make a Mavericks flash drive installer disk changed, and that is something you want to have and keep on hand.

This is not about booting from the Mt Lion or Mavericks USB Installer thumb drive. It is about a Clone of OS X on a USB 3 drive and not being able to Boot from it.

Has this been fixed yet? I paid 3k for my i7 3.5 27" with all the bells and whistles and I'm completely disappointed that my cloned hard drive won't boot from my 3tb USB 3.0 WD drive. I tried everything multiple programs zeroing out and nothing has worked. It mounts fine, can switch it to the start up drive. I can even hold down option key and see both drives and two recovery partitions. I can only boot from the internal drive, selecting the external drive just hangs. No loading or even attempted loading. no circle either showing it's loading, just a white screen that hangs for 5 mins then defaults back to my internal drive.

I'm really surprised this hasn't been fixed in mavericks, come on apple! I paid top dollar for my computer fix this big already!

I'm not but could be the person with the top of the line iMac.

It would be good have a fix or clarification from Apple. I would not have bought a computer with a 3TB internal drive that could not be cloned to a USB3 drive. USB2 is just too slow and Thunderbolt far too expensive; I bought a new 4TB USB drive for cloning the internal drive.

I have just done extensive tests and now have absolutely clear results.

Most recent Macs have USB3 ports, and USB3 is fully supported in Mac OS, but the boot ROM of some of those Macs (including my Macbook Pro mid 2012) does NOT support USB3. At least one person above has apparently been able to boot via USB3, so this limitation must not be in all models.

So you can use USB3 to clone your internal drive, and for Time Machine backups (If you use the paid version of Super Duper, you can store both on the same drive). But when you want to boot from the clone you have made, you need to connect the drive as a USB2 drive either by connecting it through a USB2 hub or by using a USB2 cable. (For typical USB3 portable drives you probably need a Micro USB2 cable, like many android phones use, to connect without a hub).

If you are like me, you update your external drive much more often than you boot from it. So USB3 does give a significant speed advantage.

I have reported this to Apple but so far Apple has not said whether or not they intend to add USB3 support to the boot ROMs that do not now have it. If enough people complain, maybe they will fix it.

I have several large Seagate USB 3 drive that have been cloned with Superduper from a new 27" iMac. They will not boot the iMac without using a USB2 cable or hub. I purchased a Seagate Thunderbolt drive that boot as it should. I took the iMac and the TB drive to the genius bar for another issue and explained why I bought the drive. The Genus said they boot customer's computers from USB drives all day long. He did it on my computer. I forgot to ask the drive's brand.

I trust you have a clone on a secondrive so that when that drive crashes there will still be a good backup.

They are probably using USB 2 external drives. They will work All Day Long.

Take it back to the store with your USB3 drives and ask them to boot your iMac from either of them. Then ask them to fix the issue.

panoramaBobl, Bob Thompson2 wrote:

I have several large Seagate USB 3 drive that have been cloned with Superduper from a new 27" iMac. They will not boot the iMac without using a USB2 cable or hub. I purchased a Seagate Thunderbolt drive that boot as it should. I took the iMac and the TB drive to the genius bar for another issue and explained why I bought the drive. The Genus said they boot customer's computers from USB drives all day long. He did it on my computer. I forgot to ask the drive's brand.

I trust you have a clone on a secondrive so that when that drive crashes there will still be a good backup.

Apparently some recent Macs (2013 vintage) will boot from USB3, though it has been reported that they do not support encrypted USB3 boot drives. But I would not be at all surprised to discover that the Genius Bar was using USB2 cables, since that avoids all the USB3 issues.