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Re: [Bug-ddrescue] Reverse not working on OS X

From: Perttu Aaltonen
Subject: Re: [Bug-ddrescue] Reverse not working on OS X
Date: Sun, 29 Dec 2013 15:51:17 +0200

Hi Florian! That seems to be the best way to go. Reverse would mainly be useful 
after the first run, when the end is already transferred, to back up to the 
last error on disk. From what I understand trimming already does this sort of 
thing so maybe not a huge benefit.


On 29.12.2013, at 13.35, Florian Sedivy wrote:

> Hallo Perttu!
> It seems to me that ddrescue doesn't know the size of your disk yet and tries 
> backward from 9223 Petabytes 1 sector at a time. "-i" does not help, because 
> in a reverse run it specifies the end of operation. You COULD solve this by 
> producing an approximate log file and option "-C" (complete only). 
> BUT the better way in my opinion would be a normal run forward with "-i" set 
> to a position after the bad beginning. This will be much faster than reverse 
> mode, which ignores copy block size and goes strictly sector by sector (as 
> far as I know). 
> On OS X use the raw device (rdisk) and "-c 256" or more for better read 
> performance. 
> Greetings, Florian 
> Am 29.12.2013 um 01:21 schrieb Perttu Aaltonen <address@hidden>:
>> Hi,
>> I use ddrescue for every defective disk, great piece of software! I mainly 
>> use ddrescue on OS X. Lately I've been trying to use the reverse-option for 
>> disks that have most of their bad sectors in the beginning. For some reason 
>> this isn't working. The position for rescue isn't right and nothing gets 
>> transferred. For example, on a 320 GB disk I tried this the epos & opos are 
>> shown as "9223 PB", even if I use the "-i" option to tell to start from a 
>> certain position. The "time since last succesful read" only gets longer and 
>> nothing transfers. I'm testing on OS X 10.7.5, ddrescue 1.17 installed from 
>> MacPorts.
>> Br,
>> Perttu
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