How to partition an external drive using Disk Utility

Outlook users that need to rebuild their Identities that do not have enough free space on their internal drives will need to use an external drive with enough free space for the rebuild.  I recommend a minimum of 300 GB free.

If you purchase a new drive, be sure to format it first using Disk Utility as Mac OS X Journaled. The drive must be formatted as GUID Partition Table to be bootable. I would not partition and use the entire new drive for the rebuild. You can always add a partition if needed after you complete the rebuild.

If you have an external drive that already has files on it but does have enough free space, use these steps to add a partition for the rebuild.

Using Disk Utility, select your external drive and add the largest partition available. I suggest a minimum of 300GB free.

  • Open Disk Utility
  • Select the disk where you want to create a new partition and click Partition
  • Select an existing partition in the Volume Scheme list, and click Add (+). Disk Utility splits the partition into two, leaving the data from that partition in one of the new partitions. If the partition is less than half-full, Disk Utility creates two partitions of equal size. Otherwise, it creates one partition large enough for the data, and another partition with the remaining space.
  • Resize the partitions as needed. You can drag the dividers between the partitions in the Volume Scheme list, or you can select a partition in the Volume Scheme list, and then enter a value in the Size field.
  • If this drive has never been used, choose a format. Select a filesystem type (Mac OS Extended Journaled is default). The drive must be formatted as GUID Partition Table to be bootable.
  • Click Apply.
  • See Disk Utility Help for additional info.

When I made my recovery partition, I used my Seagate 2TB that holds my clone backups for old OS X installs. I added a partition by selecting the bottom partition “Virtual” by clicking on the + sign.  If you no longer wish to keep this partition after recovering, you can remove and give the space back to the drive.