Re: [Bug-ddrescue] Sparse and preallocate questions/feature idea

[Antonio Diaz Diaz]

Hello.

Zeniff Martineau wrote:
> Does ddrescue estimate how sparse an output file will be when using
> --preallocate?

No, because estimating sparseness is not trivial for files and not 
possible for drives.


> If not, I'd like to suggest it as an option to do so and output the
> expected output file size.
>
> Maybe it can do so without even trying to write an image, like a dry-run?

A dry-run on a failing drive just to estimate the amount of sparseness? 
Does not sound good.


> I'm also curious about how it could be done. I think find(1) utility
> can look at sparseness of files, but how about the free space on a
> drive?

AFAIK, reading the whole drive is the only way to know the amount of 
sparseness of the resulting file.


Regards,
Antonio.