[rescue] expanding a ZFS pool: leave slack space?

[Mouse]

> The number of sectors for a given capacity disk is standardised, and
> has been for over a decade: [...]

Somewhat reassuring, albeit infuriating in its own way (see below).

> Since a 4TB disk is actually slightly larger than 4TB,

Only for disk-maker-redefined values of "TB".  At least in my
experience, "4TB" disks are a smidgen under 3.6387 actual TB (the ones
I have at ready hand to check are 7814037168 (half-K) sectors).

I've never understood why disk makers haven't been slapped down for
misleading advertising.  They've even taken to putting notes like
"based on 1GB = 1 billion bytes" in tiny print in their ads, which to
me amounts to saying "we know we're being misleading, we're doing it
deliberately, and we intend to keep doing it".  I can only assume they
also intend to abuse barratry as necessary to continue being allowed to
be deliberately misleading.

I assume they started doing it to make their products sound bigger than
they are; indeed, early on, back when the difference was 2.4% or
4.85+%, disk sizes were usually labeled honestly (though there's the
infamous "1.44M" floppy size...).  But even then, there were some
issues.  I once was on the phone to iomega for other reasons, back when
zip disks were a thing, and called them on their labeling a 96M disk as
100M.  They told me it was formatting overhead - which I later
confirmed (with a tech who actually knew) was a lie; actual formatting
overhead was more like 25% or 30%, nothing like as little as 4%.

I've occasionally fantasized about a RAM maker filling orders from the
likes of Seagate and WD with, for example, "32G" sticks of ram that
contain exactly 32000000000 bytes....

I, of course, continue to use the same terminology I always have:
quantifiers, to quote the Jargon File, "when used with bytes or other
things that naturally come in powers of 2", designate powers of 1024.

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