Your partition map may be incorrect.
1. Open Disk Utility and highlight the physical drive (Not the partition)
2. On the bottom framing of the window it will display information regarding the drive.
3. Look for "Partition Map Scheme"
4. If it says anything but "GUID Partition Table" your computer system will not be able to use it as a bootable drive.
If it is incorrect it will need to be changed, which in turn requires a reformat of the drive.
Lemme know if you need help changing that, or if it is already "GUID Partition Table"
The drive is formatted "GUID Partition Table."
The strange part of this is that the Startup Disk application in the System Preferences sees the Firewire, external drive's system folder and allows me to select the drive as the startup drive but then won't complete that selection at a restart. The machine defaults to the system folder in the drive installed in Bay 1. Also, the external drive mounts as a useable storage drive.
My next step is to get another firewire, external drive and see if it works. It occurs to me that it may be that this drive is defective.
I did attempt to use the startup manager by pressing and holding the Option key at restart. The external did not appear as a choice with the Manual Startup Manager even though the Startup Disk application in the System Preferences did see it.
The new external, firewire drive has Snow Leopard installed. The MacPro came with OS X version 10.2 or something. I can't remember. We have upgraded the machine regularly to keep in line with the better software versions. The original internal drive in Bay 1 also had Snow Leopard installed on it and it booted fine.
Mac Pro came with 10.4.7 or later.
There is a list of OS X builds by model.
If it shows in Startup Disk that is a good step.
I would still use Disk Utility to repair permissions on it, and probably rerun the last combo update on it.
There is no mention of the make of this external case? some - a few? don't work.
When 10.6.0 came out there were a LOT of threads and issues with units no longer working in the SL forum.
Using Option brings up Apple boot manager
Some have even had trouble using software to clone the OS to external, such as CCC.
Best bet is SuperDuper or clean install.
External drives, make sure that when you click on the drive (WDxxxxxx) it shows "GUID" in order to be used by OS X or used by TimeMachine.
The processor of this machine is a Dual-Core Intel Xeon with 6 GB of Memory.
Leopard was installed as an upgrade on the HDD that came with the MacPro and used for sometime on this machine without problem. We then upgraded to Snow Leopard and then decided to replace the original primary drive with this new, external, firewire drive. We installed Snow Leopard on the new drive and then tried to make it the startup disk. That is when we began having these problems.
I decided to send the 4T, expensive, fast, new external drive back to the store and exchange it for a slower, 2T, internal drive. Snow Leopard installed and the machine accepted the new drive as the startup disk. All is well I just don't have as big or as fast a drive as I wanted.
TThanks for the detailed explanation. What could be happening here is the 4T expensive and fast drive may not just be compatible with the main logic board of the machine. Of course there are still limitations even if its upgradeable.
Looking at the latest line up of MacPros in the store
When you perform a customize to order, the Max is 2TB. It could very well be that per HDD Bay the max that it can read and support is 2TB.
That's why yours worked.
That is another interesting theory, But I do not think it is quite correct. These really Big drives tend to have 4K blocks, which Windows has struggled with because they did not align their logical blocks to physical blocks and it can make the drive run really slowly. Macs have successfully formatted drives like that, at least as GUID drives, since at least 10.4 -- when they are directly attached inside the cabinet.
This is more likely to be a shortocming of the interface in your extenal enclosure not being able to cope with such a big drive.
The only reason the Apple store stops at 2 TB drives is that they have not tested the larger ones yet. They are often behind the curve in this area. They will test them when they feel there will be enough demand.
Message was edited by: Grant Bennet-Alder