Dear Franc,
Franc Zabkar wrote:
AIUI, modern hard drives fail with "weak heads". This means that data
recovery software should avoid hammering at bad sectors for two reasons.
AFAIK, ddrescue uses the most sophisticated algorithm in any recovery
software in order to avoid hammering at bad sectors.
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.
Changing drive parameters (for example, disabling retries at drive
level) is a complex and unportable task. There exist tools for this task
(hdparm[1], smartmontools[2]) and it would be dangerous to try to
automate the function of these tools inside ddrescue.
The Wikipedia says this about hdparm[3]:
"hdparm has a more serious drawback: it can crash a computer and make
data on its disk inaccessible if certain parameters are misused. Out of
approximately sixty-seven parameters, several are dangerous and could
result in "massive filesystem corruption" when used indiscriminately."
And the same can be said about ddrescue or any other data recovery tool.
[1] http://man7.org/linux/man-pages/man8/hdparm.8.html
[2] http://smartmontools.sourceforge.net/man/smartctl.8.html
[3] http://en.wikipedia.org/wiki/Hdparm
I plan to add some references to these tools to the ddrescue manual.
Examples of successful rescue cases using them are welcome.
Best regards,
Antonio.
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