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Old 23 March 2012, 00:40   #34
prowler
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Join Date: Aug 2008
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Quote:
Originally Posted by mr.vince View Post
I am shocked it spits out more than Disk2FDI which means Disk2FDI is worse. That's really a shame, because it's sold as a serious ingestion app with preservation background.
I am not inclined to agree with you that my findings necessarily indicate that Disk2FDI is the worse of these two utilities. A lot depends on the experience of the user.

I have found that if Disk2FDI fills a whole block of a dumped image with zeroes (most likely when a "missing sector header" is encountered), then that's a sure sign you'll not recover any meaningful data from that sector using that particular combination of disk drive and controller, whereas ReadADF would, I guess, have filled that block with randomly-generated data based solely on the noise picked up by the parallel port cable to which the program is so susceptible in the absence of anything else. In this case, the data "captured" by ReadADF can be dismissed.

However, let's now consider a less clear-cut case which occurred yesterday evening where Disk2FDI had captured some corrupted data from a sector with a checksum error and ReadADF captured more meaningful data using the same hardware (though I haven't yet fully analysed the implications of this particular example).

I have previously seen wholesale corruption of the data partway through a block in a dumped image triggered by a bad bit which was the singular cause of a persistent checksum error in that block on the disk! In this case, I was eventually able to capture more meaningful data from that disk block using KryoFlyux and another disk drive which hasn't since then repeated the same trick on another disk.

If yesterday's case turns out to be similar, then I guess that the susceptibility of the ReadADF program to the noise picked up by the parallel port cable somehow produced a cancelling, or at least dampening, effect on whatever perpetuated the corruption in the original image (though I have no knowledge of what feature KryoFlux might have which gives it this knack).

I should mention that even when this trick succeeds, it can take very many captures, a large number of which may fail, before the whole sector can be reconstructed.


Quote:
Originally Posted by mr.vince View Post
Well, the ADF itself is limiting you here when it comes to raw data that does not resolve.
I do not consider that to be an insurmountable handicap.


Quote:
Originally Posted by mr.vince View Post
Anyway, I never said it would not work; would be nice to compare it to something modern, e.g. KryoFlux.
In the short time that I have been using ReadADF, I have already found reasons which I have mentioned in this thread for comparing it to both Catweasel and KryoFlux.


Quote:
Originally Posted by mr.vince View Post
I'd really like to find out more because I know some people working with it and it would only be fair to let them know. Maybe we can PM about the images you created.
First, I need to find out more myself. Data recovery can be something of a black art. Breakthroughs don't happen very often, and when they do it can sometimes take weeks before the implications can be understood and the technique fully exploited.


Quote:
Originally Posted by mr.vince View Post
Well done!
Thanks. I appreciate that.

Last edited by prowler; 23 March 2012 at 00:56.
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