Date:  Sun, 16 Apr 2006 09:46:14 -0700
From:  "Adam Crews" <adam.crews (at mark) gmail.com>
Subject:  [coba-e:04704] Re: NuOnce Installer v4.2 Raid install with 2 SATA drives?
To:  coba-e (at mark) bluequartz.org
Message-Id:  <1486c6440604160946u72c0a72dm5bc7fc1f794f953 (at mark) mail.gmail.com>
In-Reply-To:  <20060416121602.M67048 (at mark) raqtweak.com>
References:  <6.1.2.0.0.20060414145205.04a53430 (at mark) mail.officetracker.com>	 <000a01c65ff2$33e07430$1e64a8c0 (at mark) nuonce.net>	 <1486c6440604142104v227480bej188573a9c43eb1d (at mark) mail.gmail.com>	 <20060415121813.M48190 (at mark) raqtweak.com> <44901839.20060415155848 (at mark) gmx.net>	 <20060416121602.M67048 (at mark) raqtweak.com>
X-Mail-Count: 04704

On 4/16/06, RAQTweak.com <bq (at mark) raqtweak.com> wrote:
> > this will not allow you to habe the boot partition be part of the
> > raid, because in case you want to boot off the second disk, the grub
> > information on that partition must be different.
> > I rather fancy the idea of all partitions being part of the raid.
>
> As far as I understood from a plain graphical linux install:
>
> 1) NOT having a "/boot" partition, but having that on "/", will allow you to
> run RAID1 for "/" (and thus /boot)
>

The way that gub works, it doesnt matter if you are using / or /boot. 
grub fundamentally works at a level lower than the filesystem.


> 2) HAVING a "/boot" partition will not allow you to make this RAID1.
>
> What are the pro's for having a seperate /boot partition, if you were to
> create a root that is large enough for the basic OS and kernel?
>
>

/boot started to become popular for several reasons, which are now
mostly outdated.  As disks became larger, there started to become
issues with lilo where it could not load kernels that resided outside
of the 1024 cylyndar boundary on a disk.  Also with raid tools like md
and lvm becoming popular, lilo had issues loading the kernel.  Lilo
was very slow to figure out a workaround, so people started to create
a filesystem at the beginnig of the disk and making it simple for lilo
to work.

Now that lilo has evolved, and gub has entered the scene, this is not
needed so much.  Many people will still use it and even mark /boot as
read only or not even mount it when the system is running to provide
added protection and security for the kernel.


The method I posted works because grub treats each 1/2 of the MD
device as if it was it's own disk.  with MD this works fine for
reading the disk (bad for writes, but fine for reading).
grub must be installed on the MBR for both disks, so that if one disk
is missing, the system can still read the MBR from any of the disks. 
after grub is installed, it is just a matter of tweaking the boot menu
so it tries to read from the first disk, and if that is not found, it
reads from the second one, and so on.

I have machines working and tested with raid1 for /boot with the
previously posted config.

-Adam