Re: cgd > 2T

[Robert Elz <kre%munnari.OZ.AU@localhost>]

    Date:        Fri, 27 Jun 2014 19:29:42 -0400
    From:        Greg Troxel <gdt%ir.bbn.com@localhost>
    Message-ID:  <rmi61jm0w49.fsf%fnord.ir.bbn.com@localhost>

  | So you'd need to use the "gpt" verification method, after you write it.

I considered doing that 6 months or so ago when I was setting up a new cgd
on a system that was (until then) disklabel free (GPT everywhere).

However, I was unable to locate any rational method of doing GPT validation,
other than writing the code from scratch (or stealing a copy from one of
the current users of it, and bending it to suit).  That is, I was unable to
locate any library function for reading &/or verifying a GPT label.
There is such a function for disklabels (which cgd uses).

Could someone who works with GPTs please make a version of that in libutil
(or wherever) (and perhaps use it in other places as well) - once that is
done, making cgdconfig use it would be trivial.

Having many (probably slightly different) GPT reading functions spread
throughout the system isn't the right solution.

  | You should be able to just newfs the raw /dev/cgd0d (or c).

In my case I actually wanted several filesystems inside the cgd (filesystems
are a useful abstraction in their own right, they have properties that
don't always need to be the same - just using one bit pot isn't always the
right solution).  Fortunately, in my case, the desire for GPT was purely
ego driven, the CGD wasn't so big as to insist on that, so I just gave up
and installed a disklabel instead.    It would be nice to convert it however...

kre