Re: software raid1

[Marco Gerards <mgerards@xs4all.nl>]

Carl Karsten <carl@personnelware.com> writes:

> I have been messing around with software raid1 - mirroring 2 drives -
> including the boot sectors. The goal is to be able to remove either
> drive and still have a functioning system.
>
> I realize that this is "not supported" given that "Add support for
> software RAID" is on the http://grub.enbug.org/TodoList but I have
> heard it can be done with some trickery: install grub on both drives
> and rely on the fact that /dev/hda1 and /dev/hda2 and /dev/md0 are all
> "the same thing" as long as md0 is the only one that gets written to.

RAID is more than just mirroring.  You can have striping, a RAID setup
with striping and a parity disk, etc.

And besides that, even mirroring can do more advanced stuff.  Like
speeding up loading of kernels by loading from both disks and being
more robust against broken disks.  But I do not know if this can be
realized.

> I did run into one problem:  if you have ide master and slave, and you
> pull the master, the slave dissapears and the box/bios won't see it so
> it won't boot from it.  so I am guessing I have to make each drive the
> master on a seperate ide bus so that pulling one won't take out the
> other.
>
> Before I spend too much time trying to make this work, anyone know of
> a HowTo that outlines this?

Just do not use GRUB 2. :)

--
Marco