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Subject: Re: GEOM stacking
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Václav Haisman wrote:

> journaled device, too. Will it overwrite the gmirror meta data and thus
> break the mirror or will it somehow magically work? Does each GEOM layer
> make the resulting block device one sector shorter?

No, when you create a mirror device, its size will be one sector less 
than size_of_raw_device. So when you add another GEOM class in it, the 
"last sector" will be the one before the last on the physical provider, 
and the new size will be two sectors less than physical, etc.

In other words, geoms are "nesting" in each other and each nested geom 
is one sector smaller than the one it's in.