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Re: [Bug-ddrescue] Feature request: Enhancement to man / TexInfo documen

From: Jim Harris
Subject: Re: [Bug-ddrescue] Feature request: Enhancement to man / TexInfo documentation
Date: Wed, 4 Sep 2013 15:46:23 -0400

<snip> All references to non FOSS software.




First, and most important, please allow me to complement you on one of the best and most efficient recovery utilities I have found.


Allow me to suggest the following entries be included in future documentation:

·         Within the “useful things you can do with ddrescue” part of the documentation. . .
Ddrescue is excellent for ripping unprotected CD’s and DVD’s since it will read every sector on the disk, whereas a straight “dd” bombs at the end if the copy size is larger than one sector at a time.  (And a one-sector read is slow as . . . .)

o   Example:  I have a newly received Ubuntu distribution disk that I ordered, and I like to create image, (iso), files of these disks so that if one is damaged or lost, I can recover from the image.  If I use “dd [infile] [outfile] bs=(some multiple of 2048)” then – unless the disk is EXACTLY the same multiple long – the last read fails with the potential for data being missed.  If I use ddrescue, I can choose an efficient large chunk size for the rip.  Once I reach the end of the disk, there’s an EOM (end of media) collision that causes ddrescue to back-off and make progressively smaller reads until the last 2048 bytes is read – whereupon it ends.

o   Command used:  ddrescue [option: block size = 2048 bytes] [option: blocks per initial chunk = 512] /dev/sr0 (or whatever) ./diskname.iso ./diskname.log – which assumes you’re sitting with a terminal window in the folder you want to write to.)  Note that I am not on my Linux box while I write this, and I don’t remember the exact option commands.

·         Within the “Rescue methods” of ddrescue. . . .
If you have a failed CD/DVD (I order and receive software and – more often than you would think – one or more of the disks are defective), and if you have access to multiple optical media drives, you have a better chance of recovering the bad sectors since one drive may fail to read a particular sector, but another drive might be able to squeeze the data out of it, depending on the laser frequency and the sensitivity of the laser-sensor that reads the reflected laser light.  This is especially useful if you only have one copy of a disk, and it fails when being imaged.  This has worked for me on many occasions where I have only one copy of a disk, it was ordered to help repair a customer’s system, and I don’t have time to wait for the replacement disks to arrive.


Again, let me thank you for an excellent utility and let me express my gratitude on behalf of everyone who depends on ddrescue, but has not had the time to write you personally to express their thanks.


Jim "JR" Harris
Principal Engineer / Owner

Arrowhead Computer Consulting, LLC


Some see things as they are, and ask "Why?"
I dream things that never were, and ask "Why Not".
Robert F. Kennedy


“Impossible” is only found in the dictionary of a fool.
Old Chinese Proverb


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