How To Set Up An External Hard Drive For Use With Mac OS X

When you first attach a hard drive to your Mac, it should automatically mount and be ready to use; however before relying on it, you should consider taking a couple of precautionary steps to ensure that the drive continues to work as expected.

Note: This guide is for those whose drive isn’t really working with their Mac, or those who want to set up their drive to work specifically work on OS X. By default, most drives should work with both Windows and OS X unless specified otherwise.)

By default, if you got a new external hard disk and you have not done anything to it, it will probably in the FAT32 format. This format will work fine on Mac, but it does have some limitations. For starters, FAT32 lacks journaling support which would help prevent data corruption, and lack of support for various filesystem permission. In addition, FAT32 drives usually come with the Master Boot Record partition scheme, which does not work with Apple’s CoreStorage routines, and therefore will not allow OS-supported encryption of the drive (among other customizations).

If your external hard drive is not working as expected, or you need it to be in Mac-specific format, here’s how to set up your hard drive for use with Mac OS X:

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To begin, be sure to format your drive. To format the drive, attach the external hard drive to your system and open Disk Utility, and then perform the following steps:

1. Select your drive device in the list of devices in the left-hand pane, which is the itemĀ above any storage volumes on the drive, and which may show the manufacturer name, media size, and so on.

2. Choose the “Partition” tab the appears.

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3. Select “1 Partition” from the drop-down menu (or more, if you have specific need for more than one volume). When you select a new partition layout from the drop-down menu, each new partition will automatically be formatted to Mac OS Extended (Journaled) by default, but be sure to double-check this by selecting each in the partition diagram and then choosing the format for it.

4. Click the Options button and ensure “GUID” is selected as the partition scheme.

5. Click Apply to save the changes.

Once you have completed all the above steps, the drive should unmount and remount with the new formatting settings, and should now be ready for use. Generally a format of the drive in this manner is all that is needed; however, some people may wish to test drives further to make sure the media does not contain any bad blocks or other errors beyond the scope of the drive’s formatting.

If you want to in-depth test your drive before you start using it, select the volume, then click “Secure Erase” in the Erase tab, and drag the Secure Erase slider to the second position before clicking OK. This will cause each available data block to be accessed and written to. If one is bad, then the disk will allocate a spare block in its place and ensure that the logically writeable storage space is available for use. Secure Erase and other similar options that test each storage block of a device may take a number of hours to complete, but it reduces the number of potential problems with the drive.

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