Linux Boot + Root + Raid + Lilo : Software Raid mini-HOWTO

Posted on 4:22 PM by Bharathvn

This document provides a cookbook for setting up root raid using the
0.90 raidtools for bootable raid mounted on root using standard LILO.
Also covered is the conversion of a conventional disk to a raid1 or
raid5 mirror set without the loss of data on the original disk.
______________________________________________________________________

Table of Contents


1. Introduction

1.1 Acknowledgements
1.2 Bugs
1.3 Copyright Notice

2. What you need BEFORE YOU START

2.1 Required Packages
2.2 Where to get Up-to-date copies of this document.
2.3 Documentation -- Recommended Reading
2.4 RAID resources

3. Bootable Raid

3.1 Booting RAID 1 with standard LILO
3.2 Detailed explaination of lilo.conf for raid boot

4. Upgrading from non-raid to RAID1/4/5

4.1 Step 1 - prepare a new kernel
4.2 Step 2 - set up raidtab for your new raid.
4.3 Create, format, and configure RAID
4.4 Copy the current OS to the new raid device
4.5 Test your new RAID
4.6 Integrate old disk into raid array

5. Appendix A. - example raidtab

6. Appendix B. - SCSI reference implementation RAID5

7. Appendix C. - ide RAID10 with initrd

8. Appendix D. - ide RAID1-10 with initrd



______________________________________________________________________

1. Introduction


1.2. Bugs

Yes, I'm sure there are some. If you'd be good enough to report them,
I will correct the document. ;-)


1.3. Copyright Notice

This document is GNU copyleft by Michael Robinton

Permission to use, copy, distribute this document for any purpose is
hereby granted, provided that the author's / editor's name and this
notice appear in all copies and/or supporting documents; and that an
unmodified version of this document is made freely available. This
document is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY, either expressed or implied. While every effort
has been taken to ensure the accuracy of the information documented
herein, the author / editor / maintainer assumes NO RESPONSIBILITY for
any errors, or for any damages, direct or consequential, as a result
of the use of the information documented herein.



2. What you need BEFORE YOU START

The packages you need and the documentation that answers the most
common questions about setting up and running raid are listed below.
Please review them throughly.


2.1. Required Packages

You need to obtain the most recent versions of these packages.

· a linux kernel that supports raid, initrd

I used linux-2.2.14 nel/v2.2/> from kernel.org


· ftp://ftp.kernel.org/pub/linux/daemons/raid/alpha/
the most
recent tools and patch that adds support for modern raid1/4/5

I used http://people.redhat.com/mingo/raid-patches/




2.2. Where to get Up-to-date copies of this document.

Click here to browse the author's latest version
of this
document. Corrections and suggestions welcome!

Boot Root Raid + LILO HOWTO

Available in LaTeX (for DVI and PostScript), plain text, and HTML.

http://www.linuxdoc.org/HOWTO/Boot+Root+Raid+LILO.html



Available in SGML and HTML.

ftp.bizsystems.net/pub/raid/ tems.net/pub/raid/>



2.3. Documentation -- Recommended Reading

If you plan on using raid1/5 over raid0, please read:

/usr/src/linux/Documentation/initrd.txt



as well as the documentation and man pages that accompany the
raidtools set.


and..... Software-RAID-HOWTO.html



2.4. RAID resources

Mailing lists can be joined at:

· This one seems quiet: majordomo@nuclecu.unam.mx
send a message to subscribe
raiddev

send mail to: raiddev@nuclecu.unam.mx




· Raid development: majordomo@vger.rutgers.edu
send a message to subscribe
linux-raid

send mail to: linux-raid@vger.rutgers.edu raid@vger.rutgers.edu> (this seems to be the most active list)



3. Bootable Raid

I'm not going to cover the fundamentals of setting up raid0/1/5 on
Linux, that is covered in detail elsewhere. The problem I will address
is setting up raid on root and making it bootable with standard LILO.
The documentation that comes with the LILO sources (not the man pages)
and with the raidtools-0.90, covers the details of booting and boot
parameters as well as general raid setup - respectively.


There are two scenarios which are covered here. Set up of bootable
root raid and the conversion of an existing non-raid system to
bootable root raid without data loss.



3.1. Booting RAID 1 with standard LILO

To make the boot information redundant and easy to maintain, set up a
small RAID1 and mount it on the /boot directory of your system disk.
LILO does not know about device 0x9?? and can not find the information
at boot time because the raid sub system is not active then. As a
simple work around, you can pass LILO the geometry information of the
drive(s) and from that, LILO can determine the position of the
information needed to load the kernel even though it is on the RAID1
partition. This is because the RAID1 partition is the same as a
standard partition but with a raid super-block written at the end. The
boot raid set should fall with the first 1024 mbytes of the disk
drive. In theory the start of the raid partition could fall anywhere
in the 1024 megs, but in practice I was unable to get it to work
unless the boot-raid started at the first block of the set. This is
probably because of something dumb that I did, but it was not worth
following up at the time. Since then I've simply set up all my systems
with the boot-raid set as the first partition. I have root raid system
configurations with bootable RAID1 mounted on /boot with root raid
sets as follows: RAID1, RAID5, RAID10 & RAID1-10 ( 1 mirror + 1 raid0
set). The last has a very peculiar lilo file pair since none of the
disk geometries are the same, however, the principals are the same for
the initial boot process. The RAID10 and RAID1-10 root mounts require
the use of initrd to mount root after the boot process has taken
place. See the appendices for the configuration files for all of
these example systems.


A conventional LILO config file stripped down looks like this:


# lilo.conf - assumes drive less than 1024
boot = /dev/hda
delay = 40 # extra, but nice
vga = normal # not normally needed
image = /bzImage
root = /dev/hda1
read-only
label = Linux



A raid LILO config file pair would look like this:



# lilo.conf.hda - primary ide master
disk=/dev/md0
bios=0x80
sectors=63
heads=16
cylinders=39770
partition=/dev/md1
start=63
boot=/dev/hda
map=/boot/map
install=/boot/boot.b
image=/boot/bzImage
root=/dev/md0
read-only
label=LinuxRaid

# ---------------------

# lilo.conf.hdc - secondary ide master
disk=/dev/md0
bios=0x80 # see note below
sectors=63
heads=16
cylinders=39770
partition=/dev/md1
start=63
boot=/dev/hdc # this is the other disk
map=/boot/map
install=/boot/boot.b
image=/boot/bzImage
root=/dev/md0
read-only
label=LinuxRaid



# BIOS=line -- if your bios is smart enough (most are not) to detect
that that the first disk is missing or failed and will automatically
boot from the second disk, then bios=81 would be the appropriate entry
here. This is more common with SCSI bios than IDE bios. I simply plan
on relocating the drive so it will replace the dead drive C: in the
event of failure of the primary boot drive.


The geometry information for the drive can be obtained from fdisk with
the command:


fdisk -ul (little L)
fdisk -ul /dev/hda

Disk /dev/hda: 16 heads, 63 sectors, 39770 cylinders
Units = sectors of 1 * 512 bytes

Device Boot Start End Blocks Id System
/dev/hda1 63 33263 16600+ fd Linux raid autodetect
/dev/hda2 33264 443519 205128 82 Linux swap
/dev/hda3 443520 40088159 19822320 fd Linux raid autodetect

* note the listing of the START of each partition



3.2. Detailed explaination of lilo.conf for raid boot

The raid lilo.conf file above, commented in detail for each entry.


# lilo.conf.hda - primary ide master
# the location of the /boot directory that will be
# designated below as containing the kernel, map, etc...
# note that this is NOT the actual partition containing
# the boot image and info, but rather the device
# that logically contains this directory.
# in this example, /dev/md1 is mounted on /dev/md0/boot
disk=/dev/md0

# tell LILO which bios device to use for boot, i.e. C: drive
bios=0x80

# tell LILO the geometry of the device
# this is usually but not always the "logical"
# geometry. Check the /proc file system or watch
# the boot messages when the kernel probes for the drive
#
sectors=63
heads=16
cylinders=39770

# this is a dummy entry to make LILO happy so it
# will recognize the raid set 0x9?? and then find
# the START of the boot sector. To really see
# what this was for, read the documentation
# that comes with the LILO source distribution.
# This parameter "must" be different than the
# disk= entry above. It can be any other mdx
# device, used or unused and need not be the one
# that contains the /boot information
#
partition=/dev/md1

# the first sector of the partition containing /boot information
start=63

# the real device that LILO will write the boot information to
boot=/dev/hda

# logically where LILO will put the boot information
map=/boot/map
install=/boot/boot.b

# logically where lilo will find the kernel image
image=/boot/bzImage

# standard stuff after this
# root may be a raid1/4/5 device
root=/dev/md0
read-only
label=LinuxRaid



4. Upgrading from non-raid to RAID1/4/5

Upgrading a non-raid system to raid is fairly easy and consists of
several discrete steps described below. The description is for a
system with a boot partition, root partition and swap partition.

OLD disk in the existing system:

/dev/hda1 boot, may be dos+lodlin or lilo
/dev/hda2 root
/dev/hda3 swap


We will add an additional disk and convert the entire system to RAID1.
You could easily add several disks and make a RAID5 set instead using
the same procedure.


4.1. Step 1 - prepare a new kernel

Download a clean kernel, raidtools-0.90 (or the most recent version),
and the kernel patch to upgrade the kernel to 0.90 raid.

Compile and install the raidtools and READ the documentation.

Compile and install the kernel to support all the flavors (0/1/4/5 ?)
of raid that you will be using. Make sure to specify autostart of
raid devices in the kernel configuration. Test that the kernel boots
properly and examine /proc/mdstat to see that the raid flavors you
will use are supported by the new kernel.


4.2. Step 2 - set up raidtab for your new raid.

The new disk will be added to an additional IDE controller as the
master device, thus becomming /dev/hdc


/dev/hdc1 16megs -- more than enough for several kernel images
/dev/hdc2 most of the disk
/dev/hdc3 some more swap space, if needed. otherwise add to hdc2



Change the partition types for /dev/hdc1 and /dev/hdc2 to "fd" for
raid-autostart.

Using the failed-disk parameter, create a raidtab for the desired
RAID1 configuration. The failed disk must be the last entry in the
table.



# example raidtab
# md0 is the root array
raiddev /dev/md0
raid-level 1
nr-raid-disks 2
chunk-size 32
# Spare disks for hot reconstruction
nr-spare-disks 0
persistent-superblock 1
device /dev/hdc2
raid-disk 0
# this is our old disk, mark as failed for now
device /dev/hda2
failed-disk 1

# md1 is the /boot array
raiddev /dev/md1
raid-level 1
nr-raid-disks 2
chunk-size 32
# Spare disks for hot reconstruction
nr-spare-disks 0
persistent-superblock 1
device /dev/hdc1
raid-disk 0
# boot is marked failed as well
device /dev/hda1
failed-disk 1



4.3. Create, format, and configure RAID

Create the md devices with the commands:

mkraid /dev/md0
mkraid /dev/md1



The raid devices should be created and start. Examination of
/proc/mdstat should show the raid personalities in the kernel and the
raid devices running.

Format the boot and root devices with:

mke2fs /dev/md0
mke2fs /dev/md1


Mount the new root device somewhere handy and create the /boot direc­
tory and mount the boot partition.

mount /dev/md0 /mnt
mkdir /mnt/boot
mount /dev/md1 /mnt/boot



4.4. Copy the current OS to the new raid device

This is pretty straightforward.


cd /
# set up a batch file to do this
cp -a /bin /mnt
cp -a /dev /mnt
cp -a /etc /mnt
cp -a (all directories except /mnt, /proc, and nsf mounts) /mnt


This operation can be tricky if you have mounted or linked other disks
to your root file system. The example above assumes a very simple sys­
tem, you may have to modify the procedure somewhat.


4.5. Test your new RAID

Make a boot floppy and rdev the kernel.


dd if=kernal.image of=/dev/fd0 bs=2k
rdev /dev/fd0 /dev/md0
rdev -r /dev/fd0 0
rdev -R /dev/fd0 1



Modify the fstab on the RAID device to reflect the new mount points as
follows:

/dev/md0 / ext2 defaults 1 1
/dev/md1 /boot ext2 defaults 1 1



Dismount the raid devices and boot the new file system to see that all
works correctly.


umount /mnt/boot
umount /mnt
raidstop /dev/md0
raidstop /dev/md1
shutdown -r now



Your RAID system should now be up and running in degraded mode with a
floppy boot disk. Carefully check that you transferred everything to
the new raid system. If you mess up here without a backup, YOU ARE
DEAD!

If something did not work, reboot your old system and go back and fix
things up until you successfully complete this step.


4.6. Integrate old disk into raid array

Success in the previous step means that the raid array is now
operational, but without redundancy. We must now re-partition the old
drive(s) to fit into the new raid array. Remember that if the
geometries are not the same, the the partition size on the old drive
must be the same or larger than the raid partitions or they can not be
added to the raid set.

Re-partition the old drive as required. Example:


/dev/hda1 same or larger than /dev/hdc1
/dev/hda2 same or larger than /dev/hdc2
/dev/hda3 anything left over for swap or whatever...



Change the failed-disk parameter in the raidtab to raid-disk and hot
add the new (old) disk partitions to the raid array.

raidhotadd /dev/md1 /dev/hda1
raidhotadd /dev/md0 /dev/hda2


Examining /proc/mdstat should show one or more of the raid devices
reconstructing the data for the new partitions. After a minute or
two... or so, the raid arrays should be fully synchronized (this
could take a while for a large partition).


Using the procedure described in the first sections of this document,
set up bootable raid on the new raid pair. Hang on to that boot floppy
while setting up and testing this last step.


5. Appendix A. - example raidtab

RAID1 example described in the first sections of this document



df
Filesystem 1k-blocks Used Available Use% Mounted on
/dev/md0 19510780 1763188 16756484 10% /
/dev/md1 15860 984 14051 7% /boot

# --------------------------

fdisk -ul /dev/hda

Disk /dev/hda: 16 heads, 63 sectors, 39770 cylinders
Units = sectors of 1 * 512 bytes

Device Boot Start End Blocks Id System
/dev/hda1 63 33263 16600+ fd Linux raid autodetect
/dev/hda2 33264 443519 205128 83 Linux native
/dev/hda3 443520 40088159 19822320 fd Linux raid autodetect

# --------------------------

fdisk -ul /dev/hdc

Disk /dev/hdc: 16 heads, 63 sectors, 39770 cylinders
Units = sectors of 1 * 512 bytes

Device Boot Start End Blocks Id System
/dev/hdc1 63 33263 16600+ fd Linux raid autodetect
/dev/hdc2 33264 443519 205128 82 Linux swap
/dev/hdc3 443520 40088159 19822320 fd Linux raid autodetect

# --------------------------

# md0 is the root array, about 20 gigs
raiddev /dev/md0
raid-level 1
nr-raid-disks 2
chunk-size 32
# Spare disks for hot reconstruction
nr-spare-disks 0
persistent-superblock 1
device /dev/hda3
raid-disk 0
device /dev/hdc3
raid-disk 1

# md1 is the /boot array, about 16 megs
raiddev /dev/md1
raid-level 1
nr-raid-disks 2
chunk-size 32
# Spare disks for hot reconstruction
nr-spare-disks 0
persistent-superblock 1
device /dev/hda1
raid-disk 0
device /dev/hdc1
raid-disk 1

# --------------------------

# GLOBAL SECTION
# device containing /boot directory
disk=/dev/md0
# geometry
bios=0x80
sectors=63
heads=16
cylinders=39770
# dummy
partition=/dev/md1
# start of device "disk" above
start=63

boot=/dev/hda
map=/boot/map
install=/boot/boot.b

image=/boot/bzImage
root=/dev/md0
label=LinuxRaid
read-only

# -------------------------

# GLOBAL SECTION
# device containing /boot directory
disk=/dev/md0
# geometry
bios=0x80
sectors=63
heads=16
cylinders=39770
# dummy
partition=/dev/md1
# start of device "disk" above
start=63

boot=/dev/hdc
map=/boot/map
install=/boot/boot.b

image=/boot/bzImage
root=/dev/md0
label=LinuxRaid
read-only



6. Appendix B. - SCSI reference implementation RAID5

4 disk SCSI RAID5



df
Filesystem 1k-blocks Used Available Use% Mounted on
/dev/md0 11753770 2146076 9000678 19% /
/dev/md1 15739 885 14042 6% /boot

# --------------------------

fdisk -ul /dev/sda

Disk /dev/sda: 64 heads, 32 sectors, 4095 cylinders
Units = sectors of 1 * 512 bytes

Device Boot Start End Blocks Id System
/dev/sda1 32 32767 16368 fd Linux raid autodetect
/dev/sda2 32768 292863 130048 5 Extended
/dev/sda3 292864 8386559 4046848 fd Linux raid autodetect
/dev/sda5 32800 260095 113648 82 Linux swap
/dev/sda6 260128 292863 16368 83 Linux native - test

# ------------------------

fdisk -ul /dev/sdb

Disk /dev/sdb: 64 heads, 32 sectors, 4095 cylinders
Units = sectors of 1 * 512 bytes

Device Boot Start End Blocks Id System
/dev/sdb1 32 32767 16368 fd Linux raid autodetect
/dev/sdb2 32768 292863 130048 5 Extended
/dev/sdb3 292864 8386559 4046848 fd Linux raid autodetect
/dev/sdb5 32800 260095 113648 82 Linux swap
/dev/sdb6 260128 292863 16368 83 Linux native - test

# ------------------------

# fdisk -ul /dev/sdc

Disk /dev/sdc: 64 heads, 32 sectors, 4095 cylinders
Units = sectors of 1 * 512 bytes

Device Boot Start End Blocks Id System
/dev/sdc2 32 292863 146416 5 Extended
/dev/sdc3 292864 8386559 4046848 fd Linux raid autodetect
/dev/sdc5 64 260095 130016 83 Linux native - development
/dev/sdc6 260128 292863 16368 83 Linux native - test

# ------------------------

fdisk -ul /dev/sdd

Disk /dev/sdd: 64 heads, 32 sectors, 4095 cylinders
Units = sectors of 1 * 512 bytes

Device Boot Start End Blocks Id System
/dev/sdd2 32 292863 146416 5 Extended
/dev/sdd3 292864 8386559 4046848 fd Linux raid autodetect
/dev/sdd5 64 260095 130016 83 Linux native - development
/dev/sdd6 260128 292863 16368 83 Linux native - test

# --------------------------

# raidtab
#
raiddev /dev/md0
raid-level 5
nr-raid-disks 4
persistent-superblock 1
chunk-size 32

# Spare disks for hot reconstruction
nr-spare-disks 0
device /dev/sda3
raid-disk 0
device /dev/sdb3
raid-disk 1
device /dev/sdc3
raid-disk 2
device /dev/sdd3
raid-disk 3

# boot partition
#
raiddev /dev/md1
raid-level 1
nr-raid-disks 2
persistent-superblock 1
chunk-size 32

# Spare disks for hot reconstruction
nr-spare-disks 0
device /dev/sda1
raid-disk 0
device /dev/sdb1
raid-disk 1

# --------------------------

# cat lilo.conf.sda
# GLOBAL SECTION
# device containing /boot directory
disk=/dev/md0
# geometry
bios=0x80
sectors=32
heads=64
cylinders=4095
# dummy
partition=/dev/md1
# start of device "disk" above
start=32

boot=/dev/sda
map=/boot/map
install=/boot/boot.b

image=/boot/bzImage
root=/dev/md0
label=LinuxRaid
read-only

# ------------------------
# cat lilo.conf.sdb
# GLOBAL SECTION
# device containing /boot directory
disk=/dev/md0
# geometry
bios=0x80
sectors=32
heads=64
cylinders=4095
# dummy
partition=/dev/md1
# start of device "disk" above
start=32

boot=/dev/sdb
map=/boot/map
install=/boot/boot.b

image=/boot/bzImage
root=/dev/md0
label=LinuxRaid
read-only



7. Appendix C. - ide RAID10 with initrd

RAID1 over striped RAID0 pair.... the disks in the RAID0 sets are not
quite the same size, but close enough.



/dev/md0 is the /boot partition and is autostarted by the kernel
/dev/md1 and /dev/md3 are the two RAID0 sets autostarted by the kernel
/dev/md2 is the root partition and is started by initrd

df
Filesystem 1k-blocks Used Available Use% Mounted on
/dev/md2 118531 76485 35925 68% /
/dev/md0 1917 1361 457 75% /boot

# ----------------------------

fdisk -ul /dev/hda

Disk /dev/hda: 4 heads, 46 sectors, 903 cylinders
Units = sectors of 1 * 512 bytes

Device Boot Start End Blocks Id System
/dev/hda1 46 4231 2093 fd Linux raid autodetect
/dev/hda2 4232 166151 80960 fd Linux raid autodetect

# ----------------------------

fdisk -ul /dev/hdb

Disk /dev/hdb: 5 heads, 17 sectors, 981 cylinders
Units = sectors of 1 * 512 bytes

Device Boot Start End Blocks Id System
/dev/hdb1 17 83384 41684 fd Linux raid autodetect

# ----------------------------

fdisk -ul /dev/hdc

Disk /dev/hdc: 7 heads, 17 sectors, 1024 cylinders
Units = sectors of 1 * 512 bytes

Device Boot Start End Blocks Id System
/dev/hdc1 17 84013 41998+ fd Linux raid autodetect
/dev/hdc2 84014 121855 18921 82 Linux swap

# ----------------------------

fdisk -ul /dev/hdd

Disk /dev/hdd: 4 heads, 46 sectors, 903 cylinders
Units = sectors of 1 * 512 bytes

Device Boot Start End Blocks Id System
/dev/hdd1 46 4231 2093 fd Linux raid autodetect
/dev/hdd2 4232 166151 80960 fd Linux raid autodetect

# ----------------------------

# raidtab
#
raiddev /dev/md0
raid-level 1
nr-raid-disks 2
persistent-superblock 1
chunk-size 8
device /dev/hda1
raid-disk 0
device /dev/hdd1
raid-disk 1

raiddev /dev/md1
raid-level 0
nr-raid-disks 2
persistent-superblock 1
chunk-size 8
device /dev/hdd2
raid-disk 0
device /dev/hdb1
raid-disk 1

raiddev /dev/md2
raid-level 1
nr-raid-disks 2
persistent-superblock 1
chunk-size 8
device /dev/md1
raid-disk 0
device /dev/md3
raid-disk 1

raiddev /dev/md3
raid-level 0
nr-raid-disks 2
persistent-superblock 1
chunk-size 8
device /dev/hda2
raid-disk 0
device /dev/hdc1
raid-disk 1

# ----------------------------

contents of linuxrc

cat linuxrc
#!/bin/sh
# ver 1.02 2-22-00
#
############# really BEGIN 'linuxrc' ###############
#
# mount the proc file system
/bin/mount /proc

# start raid 1 made of raid 0's
/bin/raidstart /dev/md2

# tell the console what's happening
/bin/cat /proc/mdstat

# Everything is fine, let the kernel mount /dev/md2
# tell the kernel to switch to /dev/md2 as the /root device
# The 0x900 value is the device number calculated by:
# 256*major_device_number + minor_device number
echo "/dev/md2 mounted on root"
echo 0x902>/proc/sys/kernel/real-root-dev

# umount /proc to deallocate initrd device ram space
/bin/umount /proc
exit

# ----------------------------

contents of initrd

./bin/ash
./bin/echo
./bin/raidstart
./bin/mount
./bin/umount
./bin/cat
./bin/sh
./dev/tty1
./dev/md0
./dev/md1
./dev/md2
./dev/md3
./dev/md4
./dev/console
./dev/hda
./dev/hda1
./dev/hda2
./dev/hda3
./dev/hdb
./dev/hdb1
./dev/hdb2
./dev/hdb3
./dev/hdc
./dev/hdc1
./dev/hdc2
./dev/hdc3
./dev/hdd
./dev/hdd1
./dev/hdd2
./dev/hdd3
./dev/initrd
./dev/ram0
./dev/ram1
./dev/ram2
./dev/ram3
./dev/ram4
./dev/ram5
./dev/ram6
./dev/ram7
./etc/raidtab
./etc/fstab
./lib/ld-2.1.2.so
./lib/ld-linux.so.1
./lib/ld-linux.so.1.9.9
./lib/ld-linux.so.2
./lib/ld.so
./lib/libc-2.1.2.so
./lib/libc.so.6
./linuxrc
./proc



8. Appendix D. - ide RAID1-10 with initrd

This is a system made up of an assortment of odds and ends. The root
mounted raid device is comprised of a RAID1 made up of one RAID0 array
from odd sized disks and a larger regular disk partition. Examination
of the lilo.conf files may give you better insight into the reasoning
behind the various parameters.



/dev/md0 is the /boot partition and is autostarted by the kernel
/dev/md1 is one half of the mirror set for md2, autostarted by kernel
/dev/hda3 is the other half of the mirror set for md2
/dev/md2 is the RAID1 /dev/md1 + /dev/hda3, started by initrd

df
Filesystem 1k-blocks Used Available Use% Mounted on
/dev/md2 138381 74421 56815 57% /
/dev/md0 2011 1360 549 71% /boot

# ----------------------------

fdisk -ul /dev/hda

Disk /dev/hda: 8 heads, 46 sectors, 903 cylinders
Units = sectors of 1 * 512 bytes

Device Boot Start End Blocks Id System
/dev/hda1 46 4415 2185 fd Linux raid autodetect
/dev/hda2 4416 43423 19504 82 Linux swap
/dev/hda3 43424 332303 144440 83 Linux native

# ----------------------------

fdisk -ul /dev/hdc

Disk /dev/hdc: 8 heads, 39 sectors, 762 cylinders
Units = sectors of 1 * 512 bytes

Device Boot Start End Blocks Id System
/dev/hdc1 39 4367 2164+ fd Linux raid autodetect
/dev/hdc2 4368 70199 32916 82 Linux swap
/dev/hdc3 70200 237743 83772 fd Linux raid autodetect

# ----------------------------

fdisk -ul /dev/hdd

Disk /dev/hdd: 4 heads, 39 sectors, 762 cylinders
Units = sectors of 1 * 512 bytes

Device Boot Start End Blocks Id System
/dev/hdd1 39 118871 59416+ fd Linux raid autodetect

# ----------------------------

# raidtab
#
raiddev /dev/md0
raid-level 1
nr-raid-disks 2
persistent-superblock 1
chunk-size 8
device /dev/hdc1
raid-disk 1
device /dev/hda1
raid-disk 0

raiddev /dev/md1
raid-level 0
nr-raid-disks 2
persistent-superblock 1
chunk-size 8
device /dev/hdc3
raid-disk 0
device /dev/hdd1
raid-disk 1

raiddev /dev/md2
raid-level 1
nr-raid-disks 2
persistent-superblock 1
chunk-size 8
device /dev/md1
raid-disk 1
device /dev/hda3
raid-disk 0

# ----------------------------

cat linuxrc
#!/bin/sh
# ver 1.02 2-22-00
#
############# really BEGIN 'linuxrc' ###############
#
# mount the proc file system
/bin/mount /proc

# autostart /boot partition and raid0
/bin/raidstart /dev/md2

# tell the console what's happening
/bin/cat /proc/mdstat

# Everything is fine, let the kernel mount /dev/md2
# tell the kernel to switch to /dev/md2 as the /root device
# The 0x900 value is the device number calculated by:
# 256*major_device_number + minor_device number
echo "/dev/md2 mounted on root"
echo 0x902>/proc/sys/kernel/real-root-dev

# umount /proc to deallocate initrd device ram space
/bin/umount /proc
exit

# ----------------------------

contents of initrd.gz

./bin
./bin/ash
./bin/echo
./bin/raidstart
./bin/mount
./bin/umount
./bin/cat
./bin/sh
./dev/tty1
./dev/md0
./dev/md1
./dev/md2
./dev/md3
./dev/console
./dev/hda
./dev/hda1
./dev/hda2
./dev/hda3
./dev/hdc
./dev/hdc1
./dev/hdc2
./dev/hdc3
./dev/hdd
./dev/hdd1
./dev/hdd2
./dev/hdd3
./dev/initrd
./dev/ram0
./dev/ram1
./dev/ram2
./dev/ram3
./dev/ram4
./dev/ram5
./dev/ram6
./dev/ram7
./etc/raidtab
./etc/fstab
./lib/ld-2.1.2.so
./lib/ld-linux.so.1
./lib/ld-linux.so.1.9.9
./lib/ld-linux.so.2
./lib/ld.so
./lib/libc-2.1.2.so
./lib/libc.so.6
./linuxrc
./proc

# ----------------------------

cat lilo.conf.hda
# GLOBAL SECTION
# device containing /boot directory
disk=/dev/md2
# geometry
bios=0x80
cylinders=903
heads=8
sectors=46
# geometry for 2nd disk
# bios will be the same because it will have to be moved to hda
# cylinders=762
# heads=8
# sectors=39

# dummy
partition=/dev/md0
# start of device "disk" above
start=46
# second device
# start=39

# seem to have some trouble with 2.2.14 recognizing the right IRQ
append = "ide1=0x170,0x376,12 ether=10,0x300,eth0 ether=5,0x320,eth1"

boot=/dev/hda
map=/boot/map
install=/boot/boot.b

initrd=/boot/initrd.gz

image=/boot/zImage
root=/dev/md2
label=LinuxRaid
read-only

# ----------------------------

cat lilo.conf.hdc
# GLOBAL SECTION
# device containing /boot directory
disk=/dev/md2
# geometry
bios=0x80
# cylinders=903
# heads=8
# sectors=46
# geometry for 2nd disk
# bios will be the same because it will have to be moved to hda
cylinders=762
heads=8
sectors=39

# dummy
partition=/dev/md0
# start of device "disk" above
# start=46
# second device
start=39

# seem to have some trouble with 2.2.14 recognizing the right IRQ
append = "ide1=0x170,0x376,12 ether=10,0x300,eth0 ether=5,0x320,eth1"

boot=/dev/hdc
map=/boot/map
install=/boot/boot.b

initrd=/boot/initrd.gz

image=/boot/zImage
root=/dev/md2
label=LinuxRaid
read-only