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

[Michael Tokarev <mjt@tls.msk.ru>]

Paul Clements wrote:
> Michael Tokarev wrote:
[]
>>>> 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...

The two features are sorta independant from each other, but if
I understand Neil correctly, he wants to implement "robust
raid" (not kicking drive on the first error etc) "on top" of
the bitmap code (which somehow makes sense ofcourse).

/mjt