2008/353 [zpool autoexpand property]

[Ceri Davies]

On Sat, May 31, 2008 at 09:35:54AM -0700, Richard L. Hamilton wrote:
> > Glenn Skinner wrote:

> > > I'm nearly certain I'm failing to see the obvious, but could you
> > > explain why an administrator would ever want this
> > > property to be set to "off"?
> > 
> > If you have a mirror with non-identical disks, one will be bigger
> > than the other, even just by a few sectors. If you temporarily
> > detach the smaller one, you unexpectedly find can't attach it again
> > if the pool auto-expands to a larger size. This has hit a number
> > of people. Similarly, SVM does not expand metadevices until
> > explicitly told to do so, which I believe is a sensible default
> > and avoids this problem.
> 
> Then couldn't there be some way to change the setting to off when
> a mirror is detached?  Given your scenario, that (along with a message
> advising of the change) might be safer even if the default is off.

That was just one example.  Generally, not defaulting to performing
potentially irreversible actions should be considered a good thing.

Ceri
-- 
That must be wonderful!  I don't understand it at all.
                                                  -- Moliere
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