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ddrescue strange read behaviour

From: Marco Marques
Subject: ddrescue strange read behaviour
Date: Sun, 05 Jan 2020 08:17:59 +0000
User-agent: Internet Messaging Program (IMP) H4 (5.0.23-git)

I have been accompaning the ddrescue util for a long time but only recently I have found some strange behaviour.
 Using the 1.24 version via AUR,  although sometimes I use the 1.19 ...

In a nutshell, I am trying to rescue a SATA HDD ( already being marked by SMART in BIOS startup as failing) but I am having a bit of trouble to
recover data from it ...
I have 2 different SATA controllers ( Intel and JMicron ) , and the results are and behaviour are different for each, with this particular HDD.

Executing ddrescue with something simple as :   sudo ddrescue -d -O /dev/sdd /mnt/mk/recover recover1.map 

In the Intel once a bad read sector is found I get several "Kernel ATA" errors and ddrescue continues to try to read. Despite the fact the HDD is now "offline and out of the system", ddrescue tries to continue with no sucess.

 In the Jmicron controller I get different situation :      
Although still getting the same "Kernel ATA" errors but now ddrescue aborts with :
 "ddrescue: Unaligned read error. Is sector size correct ?"
In the 1.19 version I get a different error:  Something like "ddrescue: unable to read input medium. " So in order to proceed I have to completly shutdown the system in order to access the HDD and proceed with the data recovery .
 ( Rebooting does not allow the system to recover access to the HDD ...)
 Any comment on the different controller behaviour ?

With this specific HDD I did found some other strange behaviour where the -i flag was being ignored ... In one of the trials I call the "-i 500GiB" but ddrescue simply ignored it as it started to read from a lower value ( I confirmed it several times in the ddrescue -vv output as being the correct value) .
 Although I did not defined the "-s " flag  ...
 Is the "-s" flag mandatory ?

Although I understand that the ddrescue output is for the running operation only, Before ddrescue aborts I get "read errors: yyy " but in the next ddrescue call it becomes 0 . it would be useful to have some kind of totaliser (failed , read error ) as also have some kind of human readable info ( number of opening tries to the file ) in the mapfile related to previous ddrescue calls .

 Thanks in advance
 Marco Marques

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