Why doesn't erasing free space actually gain more GB?

Question

Level 1

51 points

Why doesn't erasing free space actually gain more GB?

I have an external hard drive that I use to store a lot of data on and, when it gets nearly full up, I want to erase some of the items that I no longer require. I've tried using the Disk Utility to just 'erase the free space'. But after doing this there is no gain in gigabytes because it shows the same capacity of gigabytes that it showed before the so-called 'erase free space' operation.

Can someone please tell me why it's called 'erase free space' if it doesn't do just that?

iMac, OS X Mountain Lion (10.8.5)

Posted on May 26, 2014 2:51 AM

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Answer 1

May 26, 2014 4:05 AM in response to makey

Erasing the free space on a drive is a security measure to make deleted items harder to find:

http://support.apple.com/kb/HT3680?viewlocale=en_US&locale=en_US

Erasing free space can't increase the space available on a drive. The only way to increase storage space it to delete or remove items on the drive.

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Answer 2

BobHarris

Level 9

53,267 points

May 26, 2014 4:34 AM in response to makey

If you need that data, then consider a larger external disk.

If the disk has stuff you can delete, look at OmniDiskSweeper (free). Google will find it for you.

Off topic: If this this data is important to you, are you backing it up, along with your Mac's boot disk?

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Answer 3

babowa

Level 9

78,109 points

May 26, 2014 7:58 AM in response to makey

Just to make sure: have you emptied the trash can while the external is plugged in? Space will not be regained until you empty the trash. And, as already mentioned, erasing space that is already "free" space will not result in space gain.

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