35 Pass Question

Lbomb2006

New Member
I have looked through all of the forum questions and FAQ's and I can not find the answer to my question. I am using the 35 Pass method and I started the process on a 150gb hard drive 12 hours ago. The Status bar moved along fairly quickly at first but the status bar has not changed for the last 5 hours or so. There are 3 bars left to go on the status bar.

Is it normal for this to be taking so long?

Is it normal for it to slow to a crawl at the end of the status bar? Is this when it is writing.

I am under a time crunch. Would it make more sense to cancel it and redo with a 7 pass? If so, how long will that take.

Or, does anyone have an estimation of how long it will take to finish this process with the 35 pass?
 

DavidHB

Active Member
I assume that you are doing a free space erase.

Your experience with a 35 pass erase is not untypical, and, depending on the way data is arranged on the drive, erasing can slow down towards the end. Broadly speaking, on any given machine erasing time is proportional to the number of passes used. Erasing time can vary markedly between machines, so it is not really sensible to make general estimates.

Even a single pass free space erase is, in my opinion, quite adequate for an ordinary user, and it is the quickest option (and also the Eraser default).

David
 

DavidHB

Active Member
Indeed. It is worth re-quoting the quote of Peter Gutmann's own views:

Gutmann himself has responded to some of these criticisms and also criticized how his algorithm has been abused in an epilogue to his original paper, in which he states [1]:

“In the time since this paper was published, some people have treated the 35-pass overwrite technique described in it more as a kind of voodoo incantation to banish evil spirits than the result of a technical analysis of drive encoding techniques. As a result, they advocate applying the voodoo to PRML and EPRML drives even though it will have no more effect than a simple scrubbing with random data. In fact performing the full 35-pass overwrite is pointless for any drive since it targets a blend of scenarios involving all types of (normally-used) encoding technology, which covers everything back to 30+-year-old MFM methods (if you don't understand that statement, re-read the paper). If you're using a drive which uses encoding technology X, you only need to perform the passes specific to X, and you never need to perform all 35 passes. For any modern PRML/EPRML drive, a few passes of random scrubbing is the best you can do. As the paper says, "A good scrubbing with random data will do about as well as can be expected". This was true in 1996, and is still true now.”


I have not used the Gutmann method for several years now, and would recommend Eraser users to change the default method for file/folder erasing from Gutmann to a 3 pass method (I use HMG IS5).

David
 

DavidHB

Active Member
The interesting thing is that the article to which you link was published as long ago as 2008, and there has, as far as I know, been no valid challenge to its findings.

I know of no technical reason why the 3 pass method I use for file erasing should be more effective than a single pass. I just like the idea of using more passes on areas of the drive that can be identified as having contained data that has been securely erased. A free space erase, because it covers much more disk space, makes it very hard (or perhaps even impossible) to identify where on the drive the sensitive data actually resided.

David
 

GregM

Member
I'm not aware of anyone boasting they can recover data from files/HDD overwritten with a single-pass.
 
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