Disks with master boot record cannot be partitioned

On OS X El Capitan and macOS Sierra, you can’t partition an outside tough drive which is M.B.R formatted. However, you may hazard erasing the exterior hard drive to GUID partition map or run Stellar Partition Manager software to control an exterior tough drive.

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If your exterior USB tough drive is MS-DOS formatted then Disk Utility (OS X El Capitan 10.11 and macOS Sierra 10.12) won’t allow you to include a partition, resize or delete partitions on the external hard disk drive. The reasons behind Disk Utility not enabling you to partition an external hard drive formatted via file mechanism other than HFS is that these drives have actually “Master Boot Record” partition system which is frequently used by the Windows Computers. To percreate partitioning actions on such outside USB difficult drives, you need to re-format the exterior storage media to GUID partition table. Only as soon as the external tough disk is formatted through OS X Journaled or GUID partition table, the Disk Utility will allow to add, resize and also delete partitions on the external difficult drive.

Case 1) Task buttons greyed out

In the listed below screenshot you deserve to watch that the necessary work button such as Add (+), Rerelocate (-) and Apply are disabled. One have the right to neither add a brand-new partition or resize, delete one more partition. However, re-formatting the external hard drive to OS X Journaled from MS-DOS and EXFAT is enabled.


Case 2) Partition button is disabled 

On selecting the partition from the parent difficult drive, the Partition tab is greyed out or disabled.


Systems – a rough approach 

The solution to partition the outside tough drive conveniently needs reformatting the whole hard drive to GUID partition i.e. OS X Journaled. Once the outside difficult disk gets erased to GUID partition map, the Disk Utility will enable all the actions to be percreated without any hassle.

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GUID Partition 

Now having the drive formatted with GUID (OS X Journaled) partition map, the Disk Utility have actually all its vital work switch activated for including, resizing and deleting partitions. Kindly see the listed below screenshot:


In the above screenshot, it is plainly visible that the GUID formatted outside USB hard drive deserve to include another partition. And not just add, yet it have the right to resize the tough drive as per convenience. In other words, the Add (+), Rerelocate (-) and also Apply butloads are allowed for action.

Erasing the external hard drive to OS X Journaled is recommended for partitioning and resizing the hard drive. However, it is not always feasible to format an MBR outside hard disk drive just to develop or resize partitions. Erasing the exterior difficult drive will cause the loss of information. Alteraboriginal, you deserve to cost-free download and activate Stellar Partition Manager software application DMG to perdevelop the jobs of adding a brand-new partition, resizing partition sizes and also also removing the partition without reformatting or erasing the external difficult drive to GUID on Mac.

How is it done? 

Below is the user-interchallenge of the Stellar Partition Manager application that has actually ‘Common_Disk’ listed in the left-hand also pane of it. This is the very same external USB tough drive that we have displayed up in above 2 cases.

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Size inhabited by the Common_Disk outside hard driveAvailable free spacesPartition-edge enables resizing the outside tough drive. You ca rise and decrease the size of the partition with the help of the partition edge. Note: Increasing the partition size is feasible only as soon as enough amount of complimentary spaces is easily accessible.Add a brand-new partitionErase the partitionRerelocate the schosen partitionStart the process

Disk Utility vs. Partition Manager

Disk Utility

Requires erasing the MBR partitioned the external difficult drive to GUID partition map.Doesn’t organises cost-free spaces for including new partitions or resizing the existing partitions.Can Mount and Unmount a partition.Cannot work on NTFS or BootCamp partition.Can’t create a bootable disk for the running OS X 

Partition Manager

Doesn’t need re-formatting of the external difficult drive.Successtotally supplies the accessible complimentary spaces on the exterior difficult drive to add a brand-new partition and also perdevelop effective resizing.Can Hide and also Reveal a partition from unauthorised accessibility.Support including, resizing and rerelocating NTFS file units. Supports resizing BootCamp partition.Can create a Bootable USB for startup disk

Undoubtedly, the Stellar Partition Manager has a lot to offer once Disk Utility does nothing to partition your MBR formatted outside USB hard disk drive. The available attributes of the partition manager software program enable all of the partitioning work to be properly enforced on an internal Apple tough drive i.e. Macintosh HD.