Re: [Bug-ddrescue] direct disk access will not read partial sector

[Antonio Diaz Diaz]

Scott D wrote:
> I am pointing out a difference between using or not using the direct 
> disk access option. If you don't use the -d option, the full sector gets 
> read and the unrequested data is removed anyway, so ddrescue already 
> does what you don't want it to do.

It is not ddrescue the one removing the data here, but the kernel. And 
that data probably comes from some file cache.


> ddrescue -d -i 2Mi -s 1Mi /dev/sda image logfile
>
> This will work since it is using the 1024 base.

To make sure the positions and sizes are a multiple of sector size you 
can use the 'b' multiplier, meaning sectors (hardware blocks):

  ddrescue -d -i 0 -s 2048b /dev/sda image logfile


> If it is really not a good idea to change ddrescue, then maybe this 
> should be stated in the manual in the direct disk access section. I had 
> to find out the hard way.

I have not yet looked at it, but at least you can be sure I'll make this 
clear in the manual.


Best regards,
Antonio.