Ric Wheeler wrote:

We still have the following challenges:

   (1) read-ahead often means that we will  retry every bad sector at 
least twice from the file system level. The first time, the fs read 
ahead request triggers a speculative read that includes the bad sector 
(triggering the error handling mechanisms) right before the real 
application triggers a read does the same thing.  Not sure what the 
answer is here since read-ahead is obviously a huge win in the normal case.

Probably the only sane thing to do is to remember the bad sectors and 
avoid attempting reading them; that would mean marking "automatic" 
versus "explicitly requested" requests to determine whether or not to 
filter them against a list of discovered bad blocks.

	-hpa