How to Resize an Existing Volume
Disk Utility allows you to resize existing volumes without losing data, but there are a few limitations. For example, Disk Utility can decrease the size of any volume, but it can increase the size of a volume only if there’s enough free space available between the volume you want to enlarge and the next volume in that partition. For practical purposes, this means that if you want to increase the size of a volume, you’ll need to delete the volume below it in the partition set. (If the volume is the last one in the set, you won’t be able to enlarge it.) To resize an existing partition volume, complete the following steps:
How to Add a Partition to an Existing Volume
You can use Disk Utility to add a new partition to an existing volume without losing any data. When adding a new partition, Disk Utility splits the selected disk in half, leaving all the existing data on the original disk but reducing its size by 50 percent. If the amount of existing data takes up more than 50 percent of the existing partition’s space, Disk Utility will resize the partition to accommodate all its current data, and then create a new partition in the remaining space. Internal drives and volumes appear in the Disk Utility sidebar. Physical drives are listed with a generic disk icon. Volumes are listed below their associated physical drive. To add a new partition to an existing disk, complete the following steps:
How to Delete an Existing Partition
In addition to adding partitions, Disk Utility can delete existing partitions. When you delete an existing partition, its associated data will be lost, but the space the partition occupied will be freed. You can use this new free space to increase the size of the next partition up. When you delete a partition to make room, it’s important to understand that partition’s location in the partition map. For example, say that you’ve partitioned a drive into two volumes named vol1 and vol2. You can delete vol2 and resize vol1 to take over the available space without losing the data on vol1. The opposite, however, is not true. Deleting vol1 doesn’t allow vol2 to expand to fill the space that vol1 use to occupy. To delete an existing partition, complete the following steps:
