Trimmed, scraped, etc

[David Morrison]

Most of the time I can just run ddrescue and it copies the disk or 
partition which I then can work on. Just occasionally, I have to get 
into the nitty-gritty and try to recover bits of the disk. At that 
point, I have to go and read the manual to refresh my memory.

One of the things I struggle with is the terms trimmed and scraped. 
These are described in section 4 about the algorithm. However, they 
are described amongst lots of other information so it is hard to get 
the concept of what they actually mean.  Even worse, there are 
forward references, eg, trimmed and scraped are referred to in the 
section on copying. So understanding requires reading the algorithm 
part 17 times :-)

So could I suggest that these terms be included in section 2 of the 
manual, Basic Concepts. I know this is difficult as they are so 
dependent on understanding what has gone before. I have tried to 
define the terms for my own use in a general way. Are they correct?

Copying: Copies blocks, skipping those that return an error or are 
slow.  May skip way beyond the problem block to escape extended 
faults???

Trimming: For each skipped block, reads from the beginning and end by 
sector to narrow down the range of faulty sectors. This can leave a 
number of good sectors between the first and last bad sector.

Scraping: Reads all the unread parts of the disk to attempt to 
recover any good sectors not detected by trimming.

Retrying: Reads every bad sector multiple times in case it is 
possible to recover some information from it.

Thanks