Inconsistent free space being reported

[jeremypeters92]

I am trying to partition my drive so I can install a second OS on my 13" MBP running 10.8.2. When I use Quick Look it reports I have 113.2 GB free on my 750 GB HD. In Disk Utility is says I have 16.8 MB when I look at the whole drive, but when I just look at the main boot partition it tells me there is 112.94 GB free. Anyone know why this happens, and how to fix it?

 

[simsaladimbamba]

How do you use QuickLook for finding out the free capacity of your boot drive?

Can you make screenshots and attach them to your next post?

 

[jeremypeters92]

These should be what you were looking for. Anything else you need to know?

 

[jhfenton]

I am trying to partition my drive so I can install a second OS on my 13" MBP running 10.8.2. When I use Quick Look it reports I have 113.2 GB free on my 750 GB HD. In Disk Utility is says I have 16.8 MB when I look at the whole drive, but when I just look at the main boot partition it tells me there is 112.94 GB free. Anyone know why this happens, and how to fix it?

It's not an inconsistency. The 16.8 MB and 112/113 GB are measuring different things.

The 16.8 MB is how much of the space on the device is unused (i.e., not included in a partition). That tiny amount was left unallocated when your drive was partitioned.

The 113 GB is the amount of space in your primary partition that is not occupied with data.

John

 

[jeremypeters92]

Thanks John, that makes sense. But when I try to make a new partition this happens.

 

[jhfenton]

It's too small a space to make an independent partition. You might be able to resize your boot partition to include that additional 16MB, but again, it's such a small area that you might not be able to get it to include that. There's a certain margin of error in the Disk Utility GUI for resizing partitions. Strangely enough, maximizing the Disk Utility window changes the scale to allow slightly more fine tuning. But 16MB is a rounding error on a 750GB drive, so it may not help. The Terminal diskutil might work, but to me, it wouldn't be worth playing with my boot drive partition to try to capture it.

FWIW, I looked at my Mac mini's boot volume--a DIY "Fusion" drive--and it shows 679.47 GB capacity, 679.47 GB used, 90 KB available. (It was a 180GB Intel SSD added to the stock 500GB HDD.) So I have a minuscule amount of unallocated space myself.

John

 

[jeremypeters92]

Wow. And I thought 16 MB was small...

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Hmmm...tried maximizing the window, that didn't work. So, what you are saying is I need to resize the boot partition to include that 16MB of space?

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Could you tell me the exact codes I would need to resize through Terminal's diskutil? I can hardly make any sense of what it is spitting out at me...

 

[jeremypeters92]

OK I did some fooling around with diskutil and managed to figure it out. Then I got this.

 

[jeremypeters92]

Ignore disk2. There isn't supposed to be a disk2.

 

[jhfenton]

I'm not a diskutil expert, but I'm guessing you can't resize the boot volume. You could try booting from an external drive and running diskutil.

The latest online man entry I could find (for Lion, but I doubt the resizeVolume command has changed much):

diskutil(8) OS X Manual Page

You can specify size "R" instead of an absolute size to grow a volume to its maximum possible size.

I would have a complete back-up/clone of my boot volume before messing with its partitions. These kind of operations run a higher-than-normal risk of catastrophic failure. And I'd question whether its worth the time and risk involved to recapture 16MB of space. (But I understand the aesthetics involved.)

John

 

[jeremypeters92]

Thanks guys, I decided to run it in VirtualBox instead Simpler that way!