Re: Is there a drive error "retry" parameter?

[Paul Clements <paul.clements@steeleye.com>]

Michael Tokarev wrote:
> Carlos Knowlton wrote:

>>>> Is there a "retry" parameter that can be set in the kernel parameters,
>>>> or else in the code itself to prolong the existence of a drive in an
>>>> array before it is considered dirty?
>>>
>>>
>>> There's no such parameter currently.  But there was several discussions
>>> about how to make raid code more robust - in particular, in case of
>>> read error, raid code may keep the errored drive in the array and mark
>>> it dirty only in case of write error.
>>>
>> That would be nice.  Do you know if anyone has done any work toward 
>> such a fix?
> 
> 
> Looks like this is a "FAQ #1" candidate for linux softraid ;)
> I tried to do just that myself, with a help from Peter T. Breuer.
> The code even worked here on a test machine for some time.
> But it's umm.. quite a bit ugly, and Neil is going to slightly
> different direction (which I for one don't like much - the
> persistent bitmaps stuff, -- I think simpler approach is better).

The persistent bitmap code has got nothing to do with read/write error 
correction. The bitmap simply keeps track of what's out of sync between 
the component drives, so you never need a full resync. On the other 
hand, read/write error correction tries to limit the conditions under 
which a drive would be kicked out of an array (thus resulting in a 
resync). Ultimately, I think we'd like to see both capabilities in md, 
though...

--
Paul