External Drive not detected as Bootable drive in Mac OS X

[Panchu]

I have a Macbook Air which is installed with OS X 10.5.8 operating system on it. I have two external hard drives which are formatted in MAC HD format. On one of the Hard drive I have installed Mac OS X Snow leopard and on the Other hard drive I have copied all the Data from the Internal Hard drive. The drive which is installed with Snow Leopard is detected by the OS X 10.5.8 as the bootable drive but the drive on which all the data is copied is not detected as the bootable drive. Why the External drive not detected as Bootable drive in Mac OS X 10.5.8? Please help

[Bon-Z]

It is possible that the external hard drive is faulty and hence it is not getting detected as the bootable drive in the Mac OS X. External drives are the most unreliable data storage device and hence storing important data on it must be avoided. There are many disk check utilities available online which can be downloaded and then installed on the computer to check the data consistency of the drive. Depending on the manufacturer of the hard drive, download the disk check utility and run in on the hard disk which is not getting detected. The utility will display all the errors which are encountered by it while running the test on the drive. If the errors are solvable, the utility will prompt you to solve the error. If the errors are unsolvable then you will have to replace the hard disk I am afraid.

[Pugsly]

Check if the drive is in Master mode. Any system cannot detect two drives in Master mode. If two hard disks are in Mastermode and connected to the same computer, it confuses the system as in from which hard drive to boot the operating system. Also sometimes it happens that the system will only detect one master drive and will not detect the other drive at all which is happening in your case. Hence only one drive should be configured in the Master mode to successfully boot the system. If the other external drive is also configured as Master, make it slave and then connect the drive to the computer.

[Theodot]

As you have only copied the contents of the Internal hard drive on the external hard drive, it will not act as a bootable drive. Copying the contains of one drive to the other does not make the Drive bootable. In order to make the drive bootable, it has to have the booting table and the boot records on the hard drive which are only created when the operating system is installed on the system. The booting table and the boot records do not get copied if the contents of the drive is copied on the other drive. Hence you will have to install the operating system on the external drive in order to make it a bootable drive.

[Barclay]

Cloning the hard drive contents will make copy all the data from one hard drive to other hard drive including the booting information which is present on the drive. There are many applications available online which can be used to clone the contents of the hard drive. Cloning the contents of the Internal hard drive on the External hard drive will make the external hard drive exact replica of the internal hard drive and then the system will detect it as the bootable device when it is connected to the computer.

[Simond]

The application which can be used for cloning the hard drive is Carbon Copy Cloner. The Carbon copy cloner can be used on the operating systems which are released later than the 10.4 version. You will just have to download and install the application on the computer. Once the application is installed on the computer it can be used to clone the contents of the hard drive. You will just have to select the source and the destination of the drive and click on the Clone button.