second pre-emptive raid: stripes and the os

[prad]

based on the excellent ideas from the first pre-emptive raid thread we
have been considering raid1+0 or raid5 for our server, but we need to
gain a better understanding of striping.

the mirror concept was easy particularly through dru's Using Software
RAID-1 with FreeBSD:
http://www.onlamp.com/pub/a/bsd/2005/11/10/FreeBSD_Basics.html?page=1

the stripe idea is creating some issues.

having gone through both geom and vinum sections of the handbook, we
are confused as to just how stripes fit in with the os. what we have
found on the web sofar is this article on the freebsdwiki:
http://www.freebsdwiki.net/index.php/RAID0,_Software,_How_to_setup

both this article and the geom docs require an installed os, from which
you create the striped device.

so if we had 4 drives da0-3, we could install the os on da0 and then
create a stripe /dev/stripe/st0 with da1-3. however, there would be no
os on there (and most of da0 would be empty). (i suppose you can dd
stuff onto st0, but that seems a bit strange.)

so in a straight striped situation with 4 physical drives, how can you
get the os on there? where does it reside? is it supposed to be striped
across the 4 drives?

or is this the wrong way to look at it. should we be directing our
thoughts to striping across partitions that we create over various
drives after the os has been installed on a small part of the first
drive?

is raid only for data or does the os get raided too?

-- 
In friendship,
prad

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