On Fri, 23 Sep 2011 10:26:53 -0600 Thomas Fjellstrom <thomas@xxxxxxxxxxxxx>
wrote:
> On September 23, 2011, NeilBrown wrote:
> > On Fri, 23 Sep 2011 02:09:36 -0600 Thomas Fjellstrom <thomas@xxxxxxxxxxxxx>
> >
> > wrote:
> > > I forgot to say, but: Thank you very much :) for the help, and your
> > > tireless work on md.
> >
> > You've very welcome .... but I felt I needed to respond to that word
> > "tireless".
> > The truth is that I am getting rather tired of md .... if anyone knows
> > anyone who wants to get into kernel development and is wondering where to
> > start - please consider whispering 'the md driver' in their ear. Plenty
> > to do, great mentoring possibilities, and competent linux kernel engineers
> > with good experience are unlikely to have much trouble finding a job ;-)
> >
> > NeilBrown
>
> Very tempting. How much work do you think it would be to add in full raid10
> reshape support? ;D (not that I'm volunteering, I don't think I could
> comprehend a lot of the raid code, at least not at this point in time
> (extenuating circumstances)).
>
RAID10 reshape is more complicated than RAID5/6 reshape because there are
more options - more combinations.
So you would probably implement a subset of possible reshapes. And then
maybe implement another subset.
Providing you have:
- a clear understanding of the intermediate state and a way to record
that state in the metadata
- a way to tell if a given block is in the 'old' layout or the 'new' layout
or 'being reshaped'
- somewhere in memory to store all the blocks that are 'being reshaped'
it should be fairly easy. RAID5/6 has a stripe-cache so the last point is
trivial. Handling that in RAID10 is probably the biggest single part of the
task.
So: not a trivial task, but not an enormous task either.... which doesn't
narrow it down very much I guess.
NeilBrown
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