How to I attach a loose/hidden partition?

[Blackvibes]

When trying to add a new partition to my drive yesterday by splitting the free space, with help of DiskUtility, it sadly got stuck. I had to force-close the application and reboot my Macbook.

When I entered Disk Utility it showed that I had a 500GB drive of which only 250GB is partitionable. The other 250GB is poof, gone, traveling in outer unknown space.

As you can see in the below screenshot, my Toshiba HDD is 500GB, while the bar shows just 285GB (250+35). The table below shows 'Capaciteit (capacity)': 500GB, "Aantal onderliggende partities (Partitions)": 2".

So where is the rest of my 500GB?

If I dive into `terminal` and use `diskutil list` it shows the stuff below. As far as I can see it does show the hidden partition.

I've got a TimeMachine backup of the drive, so I could completely format it.. but I rather don't for obvious reasons

Who can help me out?

 

[Weaselboy]

You volume has been converted to a core storage volume and cannot be resized. Open Terminal app and run the command below to turn off core storage then you should be able to resize the main volume to use all the space.

This won't erase your disk, but backup first just to be safe.

diskutil cs revert /