Transfer capacity between two partitions I have created two partitions:


System 850GB 
Data 150GB


what I actually want is:


System 200GB 
Data 800GB


...however, disk utility doesn't let me either merge these two partitions or transfer the size between them. All it lets me do is create more partitions and it doesn't allow merging partitions from System with partitions from Data.

Clicking on minus here does nothing:
This is the kind of task I would always have given to iPartition, however, it doesn't like CoreStorage drives [File Vault &amp; Fusion Drives both use this format] &amp; also it will break Drobos.

You also need the current beta before it will support El Capitan.

With all those caveats it makes it harder to recommend these days.