Erase Free Space frozen

[bennyprofane42]

So I'm using the Disk Utility to erase free space on my Macbook (running Mavericks). I had 77GB available on my 750GB drive before I started this. It got about 80% through (using the 3-pass version) and then seemingly froze on "creating secondary temp file"--and my available space had plummeted to 8GB. Because it wasn't doing anything I chose "Skip," but now it's frozen on "Skipping" (at least an hour now), with an ugly warning as to why I can't quit Disk Utility.


How do I get it to stop?

Is this just something where I have to wait a day or so?

How can I erase free space if it eats up all my free space in erasing it (which, of course, makes no sense)?

 

[grahamperrin]

all my free space in erasing it (which, of course, makes no sense)

There's sense.

Loosely speaking, a sequence of logical actions cause all free space to be overwritten in a way that suits your preferred routine for secure erase.

Use the Force Quit dialogue. Has Disk Utility stopped responding?

 

[bennyprofane42]

It finally stopped. I tried it again using the single-pass version and got the "can't create temporary file" error.

If "deleting" files actually, you know, deleted the files, this wouldn't be an issue.

 

[grahamperrin]

single-pass version and got the "can't create temporary file" error.

That's vaguely familiar, I can't recall whether it's a bug. An excuse for me to boot El Capitan and see how it behaves.

If you use Disk Utility in Mavericks to verify the volume, is the volume apparently OK?

If "deleting" files actually, you know, deleted the files

If overwriting was the default, the OS could become unexpectedly slow.

Do you ever use Secure Empty Trash? Or FileVault 2?

 

[JohnDS]

You don't have enough free space for the temporary files the Mac needs. You should never let your free space get below 15%. Archive and delete some files and don't forget to empty the trash. Then try again.

 

[grahamperrin]

You don't have enough free space for the temporary files the Mac needs. You should never let your free space get below 15%. …

That's not applicable to Apple's Erase Free Space routines.

 

[JohnDS]

OP said "t got about 80% through (using the 3-pass version) and then seemingly froze on "creating secondary temp file"--and my available space had plummeted to 8GB."

 

[grahamperrin]

It's normal for free space to drop to close to zero.

 

[bennyprofane42]

I just let it spin and spin and spin and finally, after about 15 - 20 minutes it stopped with a fail message. However, I suddenly had 4GB more free space. So apparently it works even though it tells you otherwise.

 

[grahamperrin]

… suddenly had 4GB more free space. …

Yep.

As far as I recall, in at least one secure erase procedure there's use of a sparse bundle disk image. I assume that the bands within the bundle are the default size (8 MB).

During the procedure, the conventional wisdom of maintaining a percentage (or amount) of free space becomes … somewhat negligible. As the bands are reasonably large, there's a low risk of growth/fragmentation of the B-trees. A bundle of as many bands as is appropriate and then then the OS can suddenly handle the disk image; suddenly remove all directory entries for all bands and other temporary files that were used to securely overwrite the free space.