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Old 05-22-2009, 07:34 AM   #1
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Computer Experts Can You Answer This?

This is something I have been wondering for a while. We have all heard that when you put something on your hard drive it is almost always there forever. Even if you erase it the information can almost always still be recovered. There are ways to completely erase the information, but it takes a little knowledge and effort. It is not just as quick and simple as dragging a file to your recycle bin.

So my question is this...If the information is not really erased when we just the basic drag and drop into the recycle bin, why do we need larger hard drives? Why do we run our of hard drive space?

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Old 05-22-2009, 08:43 AM   #2
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Every file saved on the hard drive has a numeric tag on it. When you save a later version of that file, the extra bit is saved in a separate location because the original file is boxed in whith other stuff thath happened in between. When you re-open a file, the computer collects all the bits with te same file number and puts them together.

When you delete a file, all you are doing is erasing the file number. The rest stays on the drive until something else overwrites it.

At least, that's how it was explained to me...
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Old 05-22-2009, 08:56 AM   #3
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My understanding Andy is that the data needs to be overwritten a number of times to really remove it. There are programs that claim to completely remove the data from your hard drive. They do this by overwriting the data many times. If overwriting it once or twice or even 10 times does not really remove it (it can be recovered by someone who knows what they are doing) then why do we need such large hard drives? If the data is still really there why can't we get away with having a 1 gig drive since the information is still there even if we think we are erasing it?
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Old 05-22-2009, 09:20 AM   #4
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The other component to this is the size of the files we store. Photos, movies, etc., and the software we load.
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Old 05-22-2009, 09:23 AM   #5
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But that is just my point Andy. Lets say, for the sake of simplicity, that we have a 1 gig drive. We then load a picture that is 1 gig. We have taken up all the space on the drive. We then erase the picture file and add another different picture that is 1 gig. Well even though we erased the first file it is still recoverable by someone who knows what they are doing, thus there is really 2 gigs of information somewhere on that 1 gig drive.

1 gig file, erased, but recoverable
+
1 gig new file currently on the drive
=
2 gigs on a 1 gig drive
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Old 05-22-2009, 09:27 AM   #6
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I am happy to keep you occupied until and actual computer expert comes along to answer your question but we have now exceeded the scope of my knowledge.

How about those Red Sox!
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Old 05-22-2009, 09:29 AM   #7
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Old 05-22-2009, 10:09 AM   #8
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Every GB has a secret shadow GB lurking beneath to store the recoverable data. Either that or what we are told requires 1GB actually only requires 1/2 GB and the other half is in reserve for erasure and recovery.

I have no idea. I'm just making this crap up. But it sounds good doesn't it?
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Old 05-22-2009, 10:11 AM   #9
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LOL when i first read your post Alix I thought you were talking about me (GB), not gigabites (GB) I am not too swift sometimes!
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Old 05-22-2009, 10:17 AM   #10
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OMG!!! I am only now able to type again. WHOO! Tears running down my face. So...are you the REAL GB or the shadow GB today???
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Old 05-22-2009, 10:18 AM   #11
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Once the item is deleted, the computer marks its spot on the drive as available, and begins to overwrite it with new data. What can still be recovered are just pieces of the old item.
In your example, both files filled the available space on the drive, so there probably wouldn't be much to recover from the old file. A 1 gig drive with a 1 gig photo uses up the entire drive. Deleting it and saving a NEW 1 gig file would use up all the space, effectively (I think) overwriting the deleted file.

Think of it this way....
Say that the file on your drive is a 400 page book. When you delete it, the computer starts to overwrite the book. So when you go to recover the deleted file,
you might only get page 32, pages 100-111, page 45, half of page 333, and pages 298-322, plus the third line from page 2 and 12 words from pages 334 and 4 words from page 400.
Once a bit of info has been overwritten, it is gone, but the parts not yet overwritten are still recoverable.

As I understand it, anyway.
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Old 05-22-2009, 10:21 AM   #12
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I understand it completely differently GF. The erasing programs that effectively erase your hard drive completely do so by over writing the data with other data many many many times. If what you were saying were true then you would only need to over write the data one time completely and then the original data would be gone forever. This is not true though. Even after the entire drive has be over written, even 3 or 4 times lets say, someone who knows how can still recover some if not all of the original data.
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Old 05-22-2009, 10:21 AM   #13
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Quote:
Originally Posted by Alix View Post
So...are you the REAL GB or the shadow GB today???
Only the shadow knows.
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Old 05-22-2009, 11:01 AM   #14
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Is overwritten data really unrecoverable? - Computerworld Blogs
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Old 05-22-2009, 11:14 AM   #15
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Interesting article. Thanks GF.
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Old 05-22-2009, 03:43 PM   #16
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when you erase or delete something you just make it invisable (unavailable for you to see). and info is writen over the top. like repainting a wall - the old paint is still under there. you would need to strip the old paint to completely remove the old paint. there are back ups of your data to be used for a system restore (when you can go back in time and restore info you lost by deleting it). you can do a government shred which chops and scatters the data but it is still there in peices.

to totally erase the drive and make nothing recoverable you need to write the drive to zeros which is like degaussing a video tape. thats how it has been explained to me.
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Old 05-22-2009, 04:57 PM   #17
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That is how I always understood it too msmofet, but if that is true then why do we need large drives. As you described, drives essentially have unlimited space since info is just piled on top of info. If that were really the case and information was not lost, but just invisible then theoretically we would be able to have a very small drive, but have much more info on it than you would think you could. That is not true though.
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Old 05-22-2009, 05:17 PM   #18
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Quote:
Originally Posted by GB View Post
That is how I always understood it too msmofet, but if that is true then why do we need large drives. As you described, drives essentially have unlimited space since info is just piled on top of info. If that were really the case and information was not lost, but just invisible then theoretically we would be able to have a very small drive, but have much more info on it than you would think you could. That is not true though.

GB, that would be true if you always deleted stuff and never used your hard drive to store files. No one does that. Our hard drives are loaded with stuff we keep, not discard.
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Old 05-22-2009, 05:23 PM   #19
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We delete stuff because we run out of space though Andy, so if it were true that data is never really removed from the hard drive then all we would have to do is put something on the drive then delete it. It would still be on the drive, but invisible. You could then put your next item on and delete it and on and on. Then you would only need to retrieve the file you need when you need it and then delete it again freeing up that space when you are done.

If the article that GF posted is correct then that explains that what we have always been told is not really true, which would make the most sense to me.
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Old 05-22-2009, 05:26 PM   #20
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I would have the opinion that once a drive is over written, very little if any of the original file is recoverable.
We format our drives when we dispose of them by slamming them against a concrete floor, so no data is recoverable. I'm not so sure that's the best way.
When we recycle, we have the company sign an agreement to erase the data and make it unrecoverable, it's corporate data.
We had 'very important person's hard drive' and it was not working. We ended up sending it out to recover files to the tune of $3500 with no guarantees. The disk was not revolving in it's case. The only way they could recover the data was to rebuild the case around the disk-I think that's what they did. They didn't try to recover data under written data and I could imagine that being incredibly expensive if the top copy was $3500.
If I wrote something I wanted to erase, I'd delete it and write over it. (the space)
I would defragment the disk, erase the thing I wanted erased, then over write the area and defragment it again. That's what I would do for my files.
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