[CentOS] Centos 4.2 and Boot/Root on RAID?

Les Mikesell lesmikesell at gmail.com
Thu Oct 20 16:44:01 UTC 2005

On Thu, 2005-10-20 at 09:59, Steve Bergman wrote:

> I have a client that insists on going with software rather than hardware 
> raid1 to save a few dollars.

Software raid some advantages of its own. 

> Can Centos 4.2 do Boot and Root on software Raid1?
> I've heard criticisms of Grub and bootable RAID.  Also, if it is not set 
> up to work out of the box, I'd like to try to talk them out of it.

It doesn't install by itself but the grub setup only has to be done
once manually.

> I've been down that road before.  If I go nonstandard, by the time I 
> actually need to boot from the second drive in an emergency, I've 
> forgotten the special procedure.

The nature of software RAID is such that you can pretend it wasn't
there and use a single drive like a single drive.  Thus, in the worst
case of a boot problem you would take whichever drive looked the
most likely to work, connect to a controller position that is
configured to boot, and do what you would do with a single drive.
That means if you had pre-installed grub on the second drive it
will just work.  If you haven't, you can boot with the install
CD in rescue mode, chroot where it tells you, and do a grub-install
just like you would with any other drive.

> (Why can't businesses just spend a few extra dollars to do things right?!)

Often it is because for the extra money, you get no extra features
except being locked into some particular vendor's product.  With
software RAID1 you can pull out any single disk and recover the
data on any machine with a similar interface type.  With a raid
controller, if the PC or controller fails you'll have to have
exactly the same model to ever access those drives again - and you
may or may not have the tools to observe the status and 'smart'
condition of the drives and to rebuild the mirrors online.

  Les Mikesell
    lesmikesell at gmail.com

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