Understanding vinum (bootstrapped vinum)

Hi,

I'd like to setup a brand new server with 2 pieces of 120GB SATA HDD.
So i have decided I'd like to mirror the entire space of these disks
with vinum. (including root)

I've goggling documentations for accomplish this, and i have find some
documents.
This is some link.

http://devel.reinikainen.net/docs/how-to/Vinum/.
<http://org.netbase.org/vinum-mirrored.html>
Bootstrapping Vinum by Robert A. Van Valzah
<http://www.freebsd.org/doc/en_US.ISO8859-1/articles/vinum/index.html>An
introduction to Vinum on FreeBSD by Rocky
<http://bsdvault.net/sections.php?op=viewarticle&artid=86>
Chapter 13 of the FreeBSD handbook: The Vinum Volume Manager, originally
written by Greg Lehey.
<http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/vinum-vinum.html>
Vinum HOWTO for two mirrored disks, by mic at netbase dot org
<http://org.netbase.org/vinum-mirrored.html>
Chapter 12 of O'Reilly's The Complete FreeBSD: The Vinum Volume Manager
<http://www.vinumvm.org/cfbsd/vinum.txt>
Replacing a failed Vinum drive
<http://www.vinumvm.org/vinum/replacing-drive.html>.
Man vinum[4|8]

These are very clear documentations, but one thing have left what i
couldn't understand.
The documents recommend me to make a vinum bsd partition on the root
spindle with a 16 blocks offset,
and then make vinum volumes as i like, but they are warned me to make a
fake root "a" partition to remain bootable
my OS. (and don't forget the extra 265 block space for vinum header).
That is ok.

The problem is why do i have to allocate the 16 block at the beginning
of the slice? (because of vinum will cut into bootstrapping. That was
the explaining)

Ok its understandable, but what about that situation when the disklabel
on the first slice looks like this:

# /dev/ad0s1:

8 partitions:
# size offset fstype [fsize bsize bps/cpg]
a: 2097152 1048576 4.2BSD 0 0 0
b: 1048576 0 swap
c: 12715857 0 unused 0 0 # "raw" part, don't edit
d: 2097152 3145728 4.2BSD 0 0 0
e: 1048576 5242880 4.2BSD 0 0 0
f: 6424401 6291456 4.2BSD 0 0 0

As it shows the "b" swap partition is located at the 0 offset . So this
partition doesn't cut into bootstrapping, and if not, why not?

Sorry for my english, and the long theoretical mail, but i'd like to
collect as information as possible, because it will worst the effort
when i find myself a data loss situation.

Thanks for any idea.

Andriko Tamas








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