Disk Utility Partitioning Controls on Your MacBook
The Disk Utility's Partitioning controls enable you to partition your MacBook's disk. If you find yourself needing another volume on a disk — or if you need to resize the total space on existing volumes on a disk — click the Partition tab within Disk Utility to display the controls. (Make sure that you select a disk and not a volume.)
From here, you can choose a volume scheme, creating anywhere from 1 to 16 volumes on a single disk.
You can’t monkey around with the partitions on a start-up disk because Mac OS X is currently running on that disk. (Think about removing your own appendix, and you get the idea.) Also, if you resize an existing volume, you may lose files and folders on that volume — Disk Utility prompts you for permission, but it’s always a good idea to back up a partition before you resize it!
To set up the partitions on a disk, follow these steps:
From the Partition pane within Disk Utility, click the disk icon (left side of the pane) that you want to partition.
Click the Partition Layout pop-up menu and choose the total number of volumes that you want on the selected disk.
To add a partition to an existing layout, click the Add button (which carries a plus sign).
Click the first volume block in the partition list (under the Partition Layout pop-up menu) to select it.
Click in the Name field and enter the name for the selected volume.
From the Format pop-up menu, choose a format for the volume.
Always use Mac OS Extended or Mac OS Extended (Journaled) from the Format menu unless you have a specific reason to use the MS-DOS File System (for compatibility with PCs running Windows) or the ExFAT File System (for compatibility with high-capacity USB flash drives).
Type a total size for this volume in the Size field.
If you’re creating multiple volumes, click the next volume block to select it and repeat Steps 4–6.
Some folks create multiple volumes so that they can boot from multiple versions of Mac OS X — like us author types.
To delete a partition from your new scheme, click the unwanted volume and then click the Delete button (which carries a minus sign) to remove it.
After everything is set to your liking, click the Apply button to begin the process.
If you suddenly decide against a partition change, click the Revert button to return to the original existing partition scheme.
The Revert button is available only before you click the Apply button!
If you have more than one partition, check out the handles separating the volumes in the partition list — they appear as dashed lines in the lower-right corner of the partition. You can click and drag these handles to dynamically resize the volumes. This makes it easy to adjust the individual volume sizes for the disk until you get precisely the arrangement you want.