Late 2013 iMac boot from external disk problem

[mogens]

I just made a Superduper (vers. 2.7.2) clone from my 3TB internal fusion drive.
First I tried with a Seagate Backup plus USB3 3TB desktop edition. Superduper finished fine, but my iMac refused to boot from the disk. Then I tried with a WD My Book Desktop storage USB3 3TB, but same thing happened.
Is there a problem with 3TB hard drives and booting on the late 2013 iMacs.
The disks seem to work fine except from the booting problem.
Disk Utility and Diskwarrior reports no problems, when I check for errors.
What's going on?

 

[SaSaSushi]

I don't think this is a matter of the size of the external drive attached nor is it a problem of the iMac. Whether a USB 3 drive will boot is dependent on the controller chip located in the drive interface on the external drive. I don't own any Seagate products but I've read some reports that the Seagate Backup Plus External 3TB does not boot USB 3 while the Seagate Backup Plus Portable 1TB will. Any Mac that has a USB 3 port can boot from it, so long as the drive controller/firmware supports it.

I have a USB 3 dual-drive cradle here which I currently have a Seagate 3TB HDD in and OS X will not boot from it.

On the other hand, I have an Inateck UASP USB 3 enclosure which will boot just fine. It's a crap shoot. If you need bootability in a USB 3 drive it's best to confirm this capability prior to purchase.

 

[mogens]

Did a little research and there seems to be a problem with bootting from USB 3 on the latest mac models. I tried to plug the WD disk into my wired keyboard, that run on USB 2 bus, and now the disk boots just fine (but it's slow).
I have an Inateck UASP dock too, and can boot from a Caviar 2GB 3.5", but not from the 3TB Barracuda from the Seagate i removed from the enclosure.

 

[yjchua95]

Did a little research and there seems to be a problem with bootting from USB 3 on the latest mac models. I tried to plug the WD disk into my wired keyboard, that run on USB 2 bus, and now the disk boots just fine (but it's slow).
I have an Inateck UASP dock too, and can boot from a Caviar 2GB 3.5", but not from the 3TB Barracuda from the Seagate i removed from the enclosure.

I don't have this problem. I booted my Buffalo HD-PATU3 1TB over USB 3.0 just fine.

I think it's the way SuperDuper made a bootable backup to your external drive and caused it to be unbootable.

Normally I just set SuperDuper to run my customized scripts (basically just a Smart Update backup) and not make a bootable backup. I have an external SSD just for the purpose of booting up externally in case the internal SSD goes toast.

 

[Fishrrman]

[[ If you need bootability in a USB 3 drive it's best to confirm this capability prior to purchase. ]]

The best way to ensure "bootability" is to use a USB3/SATA docking station instead of buying a "pre-packaged" drive that may, or may not, work.

With a dock, if the dock supports bootability, you know that ANY drive that goes into the dock will become bootable.

That said, I have seen at least one dock that was NOT bootable from firewire (the dock was a "Voyager Quad" from Other World Computing). The same dock -would- boot via USB2, however.

There is now at least one dock out there that is thunderbolt-based. Not sure if it's bootable or not. It's WAY overpriced compared to USB3 docks, and I doubt one would see much of a speed difference between thunderbolt and USB3 in any case.

For the fastest speeds, you need to buy a dock (or drive enclosure) that is specifically stated to support "UASP" (USB Attached SCSI Protocol). This takes some of the "load" off of the CPU during data transfers.

For more than a year, I've booted and run my late 2012 Mac Mini from a USB3/SATA dock. Runs great, no problems at all.

 

[mogens]

[[ If you need bootability in a USB 3 drive it's best to confirm this capability prior to purchase. ]]

The best way to ensure "bootability" is to use a USB3/SATA docking station instead of buying a "pre-packaged" drive that may, or may not, work.

With a dock, if the dock supports bootability, you know that ANY drive that goes into the dock will become bootable.

That said, I have seen at least one dock that was NOT bootable from firewire (the dock was a "Voyager Quad" from Other World Computing). The same dock -would- boot via USB2, however.

There is now at least one dock out there that is thunderbolt-based. Not sure if it's bootable or not. It's WAY overpriced compared to USB3 docks, and I doubt one would see much of a speed difference between thunderbolt and USB3 in any case.

For the fastest speeds, you need to buy a dock (or drive enclosure) that is specifically stated to support "UASP" (USB Attached SCSI Protocol). This takes some of the "load" off of the CPU during data transfers.

For more than a year, I've booted and run my late 2012 Mac Mini from a USB3/SATA dock. Runs great, no problems at all.

Sure, but have you tried booting from a 3tb disk? I can boot just fine from my 2tb disk from the inateck USB dock. The problem is related to size of the drive. I need a 3tb drive, since it's the size of my internal drive.

 

[SaSaSushi]

The best way to ensure "bootability" is to use a USB3/SATA docking station instead of buying a "pre-packaged" drive that may, or may not, work.

Here in Japan, almost all external drives and enclosures indicate OS X bootability in the specs. The same goes for docks.

For the fastest speeds, you need to buy a dock (or drive enclosure) that is specifically stated to support "UASP" (USB Attached SCSI Protocol). This takes some of the "load" off of the CPU during data transfers.

I've seen only one UASP hub advertised so far, the Vantec UGT-AH700U3, but it still hasn't been released.

Are you aware of any others? Because apparently, you lose UASP by plugging a UASP drive into a non-UASP dock and that would be a very compelling reason not to use a hub, especially if you're booting from the drive.

 

[Fishrrman]

RE post 6:
[[ Sure, but have you tried booting from a 3tb disk? I can boot just fine from my 2tb disk from the inateck USB dock. The problem is related to size of the drive. I need a 3tb drive, since it's the size of my internal drive. ]]

This dock supports 3tb drives and has UASP support as well:
http://plugable.com/products/usb3-sata-u3

I'm sure there are others, if you look for them...