[Bug-ddrescue] SMART, reallocation, and retries

[Franc Zabkar]

Dear Sir/Madam,

See the comment by "jono-ats" here:
http://forum.hddguru.com/viewtopic.php?t=26606&p=182286#p182286

AIUI, modern hard drives fail with "weak heads". This means that data 
recovery software should avoid hammering at bad sectors for two reasons. 
The first is that this accelerates the failure of weak heads, and the 
second is that the G-list (grown defect list) can fill up and overflow with 
reallocated sectors. Many HDD models from several manufacturers will 
actually disappear from BIOS or report 0 LBAs if the G-list is corrupted or 
if it overflows.

May I suggest that ddrescue disable SMART by default, if it does not 
already do so. Also I believe that there may be ATA commands that allow 
retries to be disabled at the drive level, at least in earlier versions of 
the standard.

 Read DMA Without Retries
 Read Sectors Without Retry
 Set Features Disable Retry

Perhaps Error Recovery Control (ERC) and the ATA Streaming feature set 
might be useful in the above regard.

Regards.
Franc Zabkar