gmirror on a slice uncertainty

[Harry Newton]

I've just set up a GEOM gmirror on two slices on two disks, and would
very much appreciate it if someone could validate what I've
done. General information below and questions at end. This might just
be motivated by paranoia on my part ...

Many thanks in advance

 - Harry


Background:

 - FreeBSD 6.2-STABLE
 - AMD64 & Two (2) 340GB SATA II disks

What I want to do:

 - Create two slices on each disk (20GB + 284GB)
 - / /usr /usr/src /usr/ports SWAP on first disk (/dev/ad4s1)
 - /rii /home /usr/obj /usr/local SWAP on second disk (/dev/ad6s1)

 - use gmirror(8) to use ad4s2 and ad6s2 to provide /dev/mirror/home

What I did:

 - use sysinstall(8) to create the slices:

    hydra# fdisk -vp ad4
    # /dev/ad4
    g c620181 h16 s63
    p 1 0xa5 63 41929587
    a 1
    p 2 0xa5 41929650 583207695

 - and partition ad4s1 and ad6s1:

    hydra# bsdlabel ad4s1
    # /dev/ad4s1:
    8 partitions:
    #        size   offset    fstype   [fsize bsize bps/cpg]
      a:  2097152        0    4.2BSD     2048 16384 28528
      b:  4194304  2097152      swap
      c: 41929587        0    unused        0     0         # "raw" part,
      don't edit
      d: 10485760  6291456    4.2BSD     2048 16384 28528
      e:  4194304 16777216    4.2BSD     2048 16384 28528
      f: 20958067 20971520    4.2BSD     2048 16384 28528

 - and the same for the other disk. Install FreeBSD.

 - then:

    gmirror label -v -n home ad4s2
    gmirror load
    bsdlabel -w -B /dev/mirror/home
    gmirror insert home ad6s2
    gmirror rebuild -v home ad6s2

What's concerning me ?

 - this error message about partition c:

    hydra# bsdlabel ad6s2
    # /dev/ad6s2:
    8 partitions:
    #        size   offset    fstype   [fsize bsize bps/cpg]
      a: 583207678       16    4.2BSD     2048 16384 28520
      c: 583207694        0    unused        0     0         # "raw" part,
      don't edit
    bsdlabel: partition c doesn't cover the whole unit!
    bsdlabel: An incorrect partition c may cause problems for standard
    system utilities

 - which I get on ad4s2 but not on the provided mirror:

    hydra# bsdlabel /dev/mirror/home
    # /dev/mirror/home:
    8 partitions:
    #        size   offset    fstype   [fsize bsize bps/cpg]
      a: 583207678       16    4.2BSD     2048 16384 28520
      c: 583207694        0    unused        0     0         # "raw" part,
      don't edit

 - and this line in /var/log/messages:

    WARNING: Expected rawoffset 0, found 41929650

So, what am I asking ?

 - have I set up the mirror etc correctly ?
 - what is causing the bsdlabel error messages on slice 2 ?