Macos – Erasing Mac HardDrive leaves empty space


I just booted my MacBook Pro from the install disk and ran DiskUtility from the DVD.

I selected "Erase" to erase my entire HD. Upon completion it still says that 107MB are in Use.

It claims:

232.6 GB Capacity
232.5 GB Available
107.3 MB Used
3 Number of Files

Can anyone help explain why it is not 0 MB free?


Best Answer

Some blocks on the disk are used for the low-level HFS+ filesystem data structures, the inodes, the journal, et cetera. If those terms mean nothing to you think of it as an index of which other blocks are in use or not. It's like setting aside the first page of a new empty notebook to be a table of contents.

If you're an old-timer like me, 100 MB is 5x my first hard drive size, so it sounds like a lot. But at this scale, 107 MB out of 232.6 GB is just 0.0004 of your drive capacity. Really not that much at all.

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