docs/162723: gmirror handbook instructions ate my disk

[Michael W Lucas]

>Number:         162723
>Category:       docs
>Synopsis:       gmirror handbook instructions ate my disk
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    freebsd-doc
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          doc-bug
>Submitter-Id:   current-users
>Arrival-Date:   Mon Nov 21 16:30:08 UTC 2011
>Closed-Date:
>Last-Modified:
>Originator:     Michael W Lucas
>Release:        FreeBSD 9.0-BETA2 amd64
>Organization:
none
>Environment:
System: FreeBSD bewilderbeast.blackhelicopters.org 9.0-BETA2 FreeBSD 9.0-BETA2 #12: Wed Sep 7 03:29:55 EDT 2011 mwlucas at bewilderbeast.blackhelicopters.org:/usr/obj/usr/src/sys/GENERIC amd64

Installed 9.0-RC1/i386 from CD, built & installed RC2.

>Description:

Tried to mirror my root drive as per 

http://www.freebsd.org/doc/handbook/geom-mirror.html

System did not recover from reboot, failing with:

GEOM: mirror/gm0: corrupt or invalid GPT detected.
GEOM: mirror/gm0: GPT rejected -- may not be recoverable

Further research shows that this is expected, and is a result of our
new GPT overlords

>How-To-Repeat:

>Fix:

Could we get a warning at the top of the page that says "For FreeBSD 8
and earlier. Do not use on FreeBSD 9." ?

We need updated docs, yes, but a warning in the directions would
reduce user annoyance.
>Release-Note:
>Audit-Trail:
>Unformatted: