DiskUtility – Unable to Delete or Resize Partition

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I have a 1TB external drive with two Mac OS Extended (Journaled) partitions that I would like to merge into just one single partition. They are called Backup HD and EXT HD (see pictures). I cannot resize, nor delete, the partition Backup HD, which is empty right now. How can I do it? Why can't this be done?

As you see from the first picture (1), the button with - is greyed out and I cannot remove it. However, I can remove the partition EXT HD. Should I first create a new partition Untitled on the left of Backup HD (see picture 2), copy there all data from EXT HD, delete EXT HD and then resize Backup HD?

Thanks!

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Best Answer

The pie chart used by the Disk Utility application can give an user the impression that partitions are stored in some sort of circular fashion. Actually, partitions are store linearly. The output from the command diskutil list will shows this. Also, this output will show partitions that can be hidden when viewing the contents of a drive with the Disk Utility application. Most likely your drive is arranged with the Backup HD partition occurring before the EXT HD partition. In this case, macOS offers no effective way to merge the space from the Backup HD partition into the EXT HD partition. One solution would be to backup the data on the EXT HD partition, create one large partition, then restore from the backup.

There exists third party tools which can do what you are asking in your question, but before using such a tool, you should backup your data. However, once backed up there is no need to use the third party tool.

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