On Thu, Nov 10, 2011 at 09:21:00PM -0500, Chris Mason wrote:
> On Thu, Nov 10, 2011 at 05:32:48PM -0200, Alexandre Oliva wrote:
> > Instead of preventing the removal of devices that would render existing
> > raid10 or raid1 impossible, warn but go ahead with it; the rebalancing
> > code is smart enough to use different block group types.
> >
> > Should the refusal remain, so that we'd only proceed with a
> > newly-introduced --force option or so?
>
> Hmm, going to three devices on raid10 doesn't turn it into
> raid1. It turns it into a degraded raid10.
>
> We'll need a --force or some kind. There are definitely cases users
> have wanted to do this but it is rarely a good idea ;)
I'm not sure about use cases Chris talks about, but sans those I think
we should prevent breaking raids. If user wants to downgrade his FS he
can do that explicitly with restriper. As for the relocation code
'smartness', we already have a confusing case where balancing silently
upgrades single to raid0.
Chris, can you describe those cases in detail so I can integrate and
align this whole thing with restriper before it's merged ? (I added a
--force option for some of the transitions, probably best not to add
another closely related one)
Thanks,
Ilya
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