Bootstrapping Raid 5 w/GEOM

[Stijn Hoop]

On Thu, Jul 21, 2005 at 05:11:18PM +1000, Norberto Meijome wrote:
> Hi all,
> I have a box with 4 x 120 GB EIDE drives which I want to convert to 
> FreeBSD 5.4 ( it's an old SNAP 4500 from Snap Appliance, now owned by 
> Adaptec, running a custom build of Linux)
> 
> I want to setup software Raid 5 , and I want it to affect ALL 
> partitions, including / (so if any one of the drives fails, it will 
> still boot up properly). I am planning on using GEOM, but open to 
> suggestions.
> 
> I've been searching and cant find any pointers on how to set this up 
> properly. I've been reading http://people.freebsd.org/~rse/mirror/ , but 
> this is works for RAID 1.
> 
> Could anyone offer any insights / ideas / pointers (or step by step if 
> you so feel inclined to :-) ) on how to set this up?

I don't think it's possible -- the loader doesn't know about the mirror
even in a mirrored / setup; it justs treats one of the disks of the mirror
as 'the boot disk'. It's not until the kernel is loaded that gvinum RAID-5
can do something.

So, in your case, the loader would read random RAID-5 data instead of
a kernel and refuse to boot.

IE, it's not possible until someone writes a RAID-5 capable loader.

I would advise you to either use gmirror for booting, or define a few
gvinum mirror plexes (it is possible to boot from a mirrored gvinum
setup although it's tricky to get right).

--Stijn

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