[Bug-ddrescue] Enhancement Request: Display Error Information in Passes 1-3, check -A functionality

[Shahrukh Merchant]

On 2017-10-11 8:23 AM, Antonio Diaz Diaz wrote:
> Hello Shahrukh,

> > Change the ddrescue output format when using the fillmode-with-location

> Thanks. This sounds interesting. I'll see how it can be implemented.

Thanks Antonio for the feedback. This was my main observation on 
ddrescue after using it as it would have had the most tangible benefit.

There were two other observations that were more useability issues, but 
as long as you're going to touch the code to try to get in my previous 
suggestion, let me mention them, although I consider them less 
important, and likely more work to implement as well. (I changed the 
subject line to reflect the new items.)

1. LACK OF ERROR INFORMATION TILL PASS 4

When ddrescue does its first pass (which can take several hours on a 1 
TB drive), NO error information is provided. In fact the error count 
misleading stays at zero even though bad sectors were found, as 
evidenced by the fact that ddrescue did not terminate after Pass 1.

In fact no error information starts being displayed till Pass 4 onwards 
(Trimming Failed Blocks and then Scraping Failed Blocks). I've seen many 
articles that mention ddrescue where users were confused about this (got 
super optimistic, "Hey it's 95% done in 4 hours and no errors!!"), and 
in fact this happened with me too.

My suggestion would be that a running counts of "Errored blocks skipped" 
with a Sector or Byte count contained therein be displayed during Passes 
1-3 as well, so that users are aware of data blocks not (yet) recovered 
as soon as errors are encountered. (They then have the immense 
satisfaction of seeing the unrecovered byte count decrease dramatically 
on subsequent passes!)

It's not serious as it can be "documented away" ("Hey, just wait till 
Pass 4 before jumping to conclusions") but it would make it more 
user-friendly.

2. -A OPTION DOESN'T SEEM TO DO ANYTHING

Even though I had errored blocks, which -A is supposed to mark as unread 
and which should then trigger a reread of those blocks (in a 
pre-scraping mode?), in fact it seemed to do nothing. Ddrescue exited 
immediately giving the same status as before without having touched 
anything. It didn't change the mapfile, didn't attempt any reads, nothing.

I used -r 1 to rescrape instead, which seems subtly different to -A and 
it was good enough for me so I didn't pursue the -A issue further.

Shahrukh