HOW TO FORMAT EXTERNAL DISK FOR MacBook Air

Drive Preparation

1. Open Disk Utility in your Utilities folder.

2. After DU loads select your hard drive (this is the entry with the mfgr.'s ID and size) from the left side list. Click on the Partition tab in the DU main window.

3. Under the Volume Scheme heading set the number of partitions from the drop down menu to one. Set the format type to Mac OS Extended (Journaled.) Click on the Options button, set the partition scheme to GUID then click on the OK button. Click on the Partition button and wait until the process has completed.

4. Select the volume you just created (this is the sub-entry under the drive entry) from the left side list. Click on the Erase tab in the DU main window.

5. Set the format type to Mac OS Extended (Journaled.) Click on the Security button, check the button for Zero Data and click on OK to return to the Erase window.

6. Click on the Erase button. The format process can take up to several hours depending upon the drive size.

Steps 4-6 are optional but should be used on a drive that has never been formatted before, if the format type is not Mac OS Extended, if the partition scheme has been changed, or if a different operating system (not OS X) has been installed on the drive.

Use Disk Utility and if it's only going to be used on the MBA format as Mac OS Extended (Journaled). Here is a link with some step by step instructions.

THanks a lot rkau. it worked very well..

First back up your data on you external hard drive as we are going to erase the disk in this process.

1. Open up disk utilty
2. then select your drive name (the drive name shoud be indexed)
3. Go to the erase tab
4. then choose the format on the drop down menu
5. then if you are abosoutly sure you backed up your data, then hit erase

Here are what some formats are best used for:

mac os extended (journaled) - optimized for mac use. Not compatible with windows or linux.

MS-DOS(FAT32) - compatible with windows. Copying data on mac to external hard drive with this format will make copying much longer.

ext4- compatible with linux and (mabye) windows. Same thing as MS-DOS(FAT 32). Slow copying.