On Mon, Aug 29, 2011 at 11:40:34PM -0400, Edward Ned Harvey wrote:
> > On Sat, Aug 27, 2011 at 08:44:13AM -0700, Richard Elling wrote:
> > > I'm getting a but tired of people designing for fast resilvering.
> > 
> > It is a design consideration, regardless, though your point is valid
> > that it shouldn't be the overriding consideration.
> I disagree.  I think if you build a system that will literally never
> complete a resilver, or if the resilver requires weeks or months to
> complete, then you've fundamentally misconfigured your system.  Avoiding
> such situations should be a top priority.  Such a misconfiguration is
> sometimes the case with people building 21-disk raidz3 and similar
> configurations...

Ok, yes, for these extreme cases, any of the considerations gets a
veto for "pool is unservicable". 

Beyond that, though, Richard's point is that optimising for resilver
time to the exclusion of other requirements will produce bad designs.
In my extended example, I mentioned resilver and recovery times and
impacts, but only in amongst other factors.

Another way of putting it is that pool configs that will be pessimal for
resilver will likely also be pessimal for other considerations
(general iops performance being the obvious closely-linked case).


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