Faster recovery from a disk with bad sectors

Solution 1:

First, for the software to use: you could try using ddrescue instead of dd.

ddrescue has a switch to do only a limited number of retries. It can also use a logfile, so it records which blocks were bad. If you later feel like doing more retries, you can use the same logfile to run ddrescue again with different options (like more retries) and it will retry only the necessary blocks.

Example usage:

# ddrescue -n /dev/sda /dev/sdb rescue.log
# ddrescue -r1 /dev/sda /dev/sdb rescue.log

From the ddrescue info-page:

   -n, --no-scrape     
          Skip the scraping phase. Avoids spending a lot of time
          trying to rescue the most difficult parts of the file.

   -r, --retry-passes=<n>
          Exit after given number of retry passes. Defaults to 0.
          -1 means infinity. Every bad sector is tried only once 
          in each pass. To retry bad sectors detected on a previous
          run, you must specify a non-zero number of retry passes.

Here are some additional sources to using ddrescue:

• info ddrescue
• http://www.forensicswiki.org/wiki/Ddrescue

Edit

In case the HDD itself is taking too long, you can try to enable a feature called TLER (Time Limited Error Recovery) or CCTL (Command Completion Time Limit). Not all HDDs have it, but you can use it to limit the time on the HDD controller itself. This approach can be combined with using ddrescue, of course.

Linux has a tool called smartctl (in the smartmontools package).

To check the current setting ("disabled" means an unlimited time, which you do not want):

# smartctl -l scterc /dev/sda

To set it to a fixed value (5.0 seconds in this example. Setting it to 0 disables TLER):

# smartctl -l scterc,50,50 /dev/sda

Source for TLER: http://en.wikipedia.org/wiki/TLER

Solution 2:

For a fast and quick option to rescue the disc you can use a sh script file and run the file with sh. It contains this line, just repeat sudo ddrescue and sleep 3 few more times. The sleep is used to make the drive rest some seconds:

#! /bin/sh -e 
sudo ddrescue -d -r0 -e +0 -T 1s -n /dev/drivepartition file.img log.logfile 
sleep 3

The options used above:

• -r0 : with no retries
• -e +0: exit on first error
• -T 1s: exit with 1 second fail read
• -d : Direct I/O
• -n : no scrape

You can use -R after finish with option -A once, that will reverse and remove all errorsize and start again backwards. Means it will read errors differently.