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From: Robbie Hatley on 28 Jul 2010 03:25

On 5/4/2010, Robert Heller wrote:

> At Tue, 04 May 2010 12:41:25 -0700 Robbie Hatley wrote:
>
> > ... What I need to do is to just break a Linux software RAID array,
> > preferably without interfering with *any* of the existing operating
> > systems. Does anyone here know how to do that? ...
>
> ... use mdadm to remove the second disk ...

No mdadm, or any other RAID admin tool exists in Red Hat 9. The devs
apparently figured its software RAID doesn't need administering, so they
conveniently provided no way to do any administering.

No problem, though, I just launched Win2K, ran PowerQuest PartitionMagic,
deleted the 2nd partition of the RAID-1 array (hdb6), and created a new
hdb6 partition of type FAT32 (aka "vfat" in Linux, apparently). I put
some files there, and on restarting in Linux, I was able to
mount -t vfat /dev/hdb6 /mnt/Liaison
and access files on the new partition.

Basically, my "/" folder is now a RAID-1 array with only one array
element. It works, but gives some odd error messages which flit by
on startup, like "Broken RAID array! Cannot reconstruct array!"
or some such.

So the question is, can I convert "/" to just a plain ext3 file type?
(I'm assuming /dev/hda7 is ext3 under the hood, because /dev/md0 is
ext3. This assumption might be false.)

my /etc/fstab looks like so:

LABEL=/boot /boot ext3 defaults 1 2
/dev/md0 / ext3 defaults 1 1
/dev/hda6 swap swap defaults 0 0
/dev/hda2 /mnt/Ambrose msdos user 0 0
/dev/hdb6 /mnt/Liaison vfat user 0 0
none /dev/pts devpts gid=5,mode=620 0 0
none /proc proc defaults 0 0
none /dev/shm tmpfs defaults 0 0
/dev/cdrom /mnt/cdrom udf,iso9660 noauto,owner,kudzu,ro 0 0
/dev/fd0 /mnt/floppy auto noauto,owner,kudzu 0 0

To substitute the element for the array, I'm assuming I'd need to do
at least the following 3 things:

1:
Change line 2 of fstab
from
/dev/md0 / ext3 defaults 1 1
to
/dev/hda7 / ext3 defaults 1 1

2:
Change line 15 of /boot/grub/grub.conf
from
kernel /vmlinuz-2.4.20-6 ro root=/dev/md0 hdc=ide-scsi hdd=ide-scsi
to
kernel /vmlinuz-2.4.20-6 ro root=/dev/hda7 hdc=ide-scsi hdd=ide-scsi
so that Grub looks for / on /dev/hda7 instead of /dev/md0.

3:
Change the partition table entry for hda7 from "software RAID component" to "ext3".

I'm not sure any of the above is going to work, though, because I'm not 100%
certain that Red Hat 9 software RAID even works that way. Does anyone here
know for sure whether or not data on Red Hat 9 software RAID-1 array elements
is written in ext3 format, and whether substituting an element for the array
would even work?

Or should I stop while I'm ahead and just stick with the broken array?

(One reason I want to get away from the broken array if possible is that
I'm thinking that having / be a straight ext3 partition would simplify
upgrading to a more modern version of Linux.)

--
Cheers,
Robbie Hatley
lonewolf [[at]] well [[dot]] com

From: Robbie Hatley on 28 Jul 2010 03:29

Pascal Hambourg wrote:

> Robbie Hatley a écrit :
> >
> > It's the redundant kind. Straight redundancy, no striping.
> > The idea was to provide a constant running backup of everything on
> > a separate physical hard disk
>
> Mirroring RAID does *not* provide backup. It provides availability. It
> won't protect against things such as "rm -rf /" or data corruption.

Hmmm. I'm not sure that's the best way to phrase that, but yes, you
do have a point there. RAID-1 is rather like IMAP in that regard.

IMAP provides "availability" (as you phrase it) in the sense that
if your hard disk crashes, your email archives are still on the server
and can be accessed by buying a new HD, reinstalling OS and email client,
making new a IMAP acct in the client, and synching-up. But it does *not*
protect against accidental deletion, or sabotage by an irate roommate or
a disgruntled coworker, precisely because server and client "mirror" each
other, like RAID-1.

"Backup", on the other hand, would be a static snapshot on an offline
media. Like the snapshots I make from time to time of important folders
on a separate large external hard disk.

(I don't really need "availability", and "backup" I already have; so I'm
trying to ditching my RAID-1 in favor of / being straight ext3... but
that's another story, and shall be told in another post.)

--
Cheers,
Robbie Hatley
lonewolf [[at]] well [[dot]] com

From: Chris Davies on 1 Aug 2010 16:30
Robert Nichols <SEE_SIGNATURE(a)localhost.localdomain.invalid> wrote:
> And if mounting /dev/hda7 as ext3 works, you'll want to change the
> partition type from "fd" (Linux raid auto) to "83" (Linux) so that
> the kernel won't try to find RAID information there.

That was the OP's step 3.
Chris
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