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Quick question about wiping free space vs. entire drive?


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#1 OFFLINE anon1749

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Posted 02 November 2011 - 05:50 AM

I was cleaning up an external drive the other day and thought I would give it a once over before using it again, so naturally I used CCleaner and wiped the free space. Worked great, only took 3 hours maybe? Then I decided there was nothing better going on so I ran "wipe the whole drive" now HERE is where my question comes in. Once I selected the whole drive instead of free space, it was up to 5.6 DAYS to do "the same" job. Just to clarify, when I said I cleaned up the drive, I did mean deleting everything after moving to my tower. Now I'm puzzled, why does a "free space" free space wipe take so much less time than a "whole disk" free space wipe? Any help would be great!

#2 OFFLINE Alan_B

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Posted 02 November 2011 - 07:21 AM

Free space is the space within a partition that has only deleted files or has never been used.
Wiping Free space does not wipe existing files.

Wiping a drive will over-write everything in a partition, including all files.
It MAY do far more than that depending upon which tool is in use :wacko:

I think CCleaner only wipes partitions within a Hard Disk DRIVE, and each of these is called a Drive.
I believe some tools will wipe an entire HDD, i.e. everything within partitions and also the Unallocated space between partitions.

#3 OFFLINE anon1749

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Posted 03 November 2011 - 06:07 AM

Yeah, I get that much, my question is, since the drive is already blank, WHY is there such a huge time difference no matter which option I choose?

#4 OFFLINE Augeas

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Posted 03 November 2011 - 11:25 AM

It doen't matter that the drive is 'blank', as WFS will work the same way whatever was or is on it. WFS will fill the unused space with files containing zeroes (for one pass) and then delete them. Wipe Entire Drive (I assume this is what you mean by "wipe the whole drive") will format the drive and then run a WFS. There will be a considerable difference in timing as the Wipe Entire Drive has far more to do.

Either Vista or 7 - I can't remember which - will overwrite sectors with zeroes if a full format is requested. I don't know if CC does this, or indeed what Windows version you have. A full format in this way, followed by a WFS will take even more time.

After all that I wouldn't believe the 5.6 days figure. We all know how variable and sometimes wildy wrong estimated times can be, for computers and plumbers. As an aside, are you using the same overwrite option (hopefully one pass) on both operations?

#5 OFFLINE anon1749

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Posted 06 November 2011 - 03:20 AM

@Augeas

You seriously responded better to my question than anyone has ever answered me before ahaha! If I could get answers that concise on programming forums I would have my own OS by now, but on to the topic. Yeah I didn't know that a "full format" took that long, I always did quick format so roughly 20s-1min. I did only do 1 pass but why does it really matter how many? I mean I know that 7+ is overkill unless you're a terrorist/whatever but is there an inherently bad quality about doing so? Thanks again!

#6 OFFLINE Augeas

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Posted 06 November 2011 - 04:41 AM

Thanks for the kind words (royalties would be better). One pass is suggested because it's all you need to make data unrecoverable, and multiple passes just take so long to run. Few seem to realise that overwriting a mere 30 gb of data using the dreaded 35-pass method involves writing over a terabyte of data.