Re: async writes in raid1

[Paul Clements <Paul.Clements@SteelEye.com>]

"Peter T. Breuer" wrote:
> 
> "A month of sundays ago Paul Clements wrote:"

> > * allowing the bitmap to be rescaled -- i.e., changing the amount of
> > data that each bit represents
> 
> I really don't agree with that :-).  But maybe it can be done!  It's
> just I personally see no way anyone can count in anything except 1K
> blocks with the current raid code the way it is.
> 
> Originally I wrote the patch with more generality, but realized that the
> generality could never be made use of - there are too many assumptions
> in the extant raid code that one block = 1KB.

The translation from 1K blocks to whatever-sized bitmap blocks (or
"chunks") will be done only when marking or unmarking the bitmap (and
incrementing/decrementing the block counters). The block counters allow
us to know when multiple 1K block writes are actually on the same
"chunk" so that everything is handled correctly.

--
Paul