Re: [Bug-ddrescue] ddrescue slower than dd

[Antonio Diaz Diaz]

Hello Adrien.

Adrien Cordonnier wrote:
> In short, it works much better if the partition image is on its own
> partition than in a file on a NTFS partition.

I do not use NTFS, but speed problems when using NTFS as destination 
have been reported before[1]:

"NTFS-3g eating 100%. Solved by switching to ext3".
[1] http://lists.gnu.org/archive/html/bug-ddrescue/2009-06/msg00004.html


> So I copied my image file to a partition on the same drive and proceed
> with the recovery (with option -f). Good areas were recovered at 5,3
> MB/s by ddrescue. This is not as fast as dd but was a good enough
> speed.

It is difficult for ddrescue to manage all the logfile accounting and be 
faster than dd, but it should come pretty close. Have you tried a larger 
'--cluster-size'?


> You also let me discover lzip. I understand it uses the same
> compression algorithm than the 7z file format which is what I meant
> with 7zip compression. It is now installed on my computers.

Both lzip and 7zip use different variants of the LZMA algorithm (LZMA is 
not really an algorithm; it is more like a "coding scheme"), but the 
lzip format is better suited for posix systems like GNU/Linux than 7z.


Best regards,
Antonio.