If you're running Windows under VirtualBox, you should be aware of the Windows utility "sdelete": http://technet.microsoft.com/en-us/sysinternals/bb897443.aspx There are at least 2 different ways for VirtualBox to emulate a disk drive: using a sector-by-sector copy or by using a virtual drive that doesn't bother storing sectors with all zeros. Most people use a virtual drive, but this means that "garbage" unused sectors whose contents aren't zero still take up space. If you run the Windows defragmentation utility within the virtual machine, and then run "sdelete" within the virtual machine, these "garbage" sectors will be reset to zeros, so that the virtual disk image will be much smaller. http://dotnetworkaholic.com/2013/04/06/compacting-virtual-machines-virtualbo... At 10:33 PM 8/10/2014, Bill Gosper wrote:

(Apologies for the subject matter but I really need some hand-holding here.)

On 2014-08-10 19:44, Eugene Salamin via math-fun wrote:

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Can you isolate the problem of whether the hard drive has a hardware problem?

The customer-oriented disk diagnostics are more about damaged file structure than drive performance, but that might be appropriate here. They found and fixed two damaged files and a bleepload of permissions. But they recovered negligible space, which continues to disappear.

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Can you disable Virtual Box,

Believe me, it's disabled far beyond my wishes.

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and just run normal Apple software?

-- Gene

I'm trying to. I just wrote and deleted a big file on a flash drive (heating it up!). The freed space reappeared. So if it's software, it's low-level disk driver stuff. But what could have altered it?

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________________________________ From: Henry Baker <hbaker1@pipeline.com> To: math-fun <math-fun@mailman.xmission.com> Sent: Sunday, August 10, 2014 6:39 PM Subject: Re: [math-fun] Apple bizarreness--write-once hard drive

TByte drives are really, really cheap at Costco.

Buy one & use it for Virtual Box, etc., at least for experimentation.

In this day & age, lack of HD space shouldn't ever be an issue.

Also, you can now get 64GByte flash drives that aren't quite as fast as HD's, but are fast enough for many porpoises.

Neil Bickford once repeated that "algorithms are for people who don't know how to buy RAM". So I guess file deletion is for those whose Costco membership has lapsed. --rwg

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At 06:22 PM 8/10/2014, Bill Gosper wrote:

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Not exactly math-fun, but have mercy. I just had a fruitless phonechat with an Apple nonGenius. MacBook Pro freezes and requires powerbutton reboot when Virtual Box hangs well into loading XP. OK, Apple won't touch Virtual Box, but I hoped|conjectured it was just an ungraceful consequence of only 118G of unused hard drive, so I deleted many G and emptied the trash. Now there is only 117G free. While on the phone, I sacrificed an additional 2.85G Mathematica 8.0. Free shrank a little more.

Anybody?? --rwg