How To Set Up Software RAID1 On A Running System (Incl. GRUB Configuration) (Fedora 8) - Page 3

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Submitted by falko (Contact Author) (Forums) on Fri, 2008-02-15 17:32. ::

7 Preparing /dev/sda

If all goes well, you should now find /dev/md0 and /dev/md2 in the output of

df -h

[root@server1 ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/md2              4.4G  2.4G  1.8G  58% /
/dev/md0               99M   15M   80M  16% /boot
tmpfs                 185M     0  185M   0% /dev/shm
[root@server1 ~]#

The output of

cat /proc/mdstat

should be as follows:

[root@server1 ~]# cat /proc/mdstat
Personalities : [raid1] [raid6] [raid5] [raid4]
md0 : active raid1 sdb1[1]
      104320 blocks [2/1] [_U]

md1 : active raid1 sdb2[1]
      513984 blocks [2/1] [_U]

md2 : active raid1 sdb3[1]
      4618560 blocks [2/1] [_U]

unused devices: <none>
[root@server1 ~]#

Now we must change the partition types of our three partitions on /dev/sda to Linux raid autodetect as well:

fdisk /dev/sda

[root@server1 ~]# fdisk /dev/sda

Command (m for help): <-- t
Partition number (1-4): <-- 1
Hex code (type L to list codes): <-- fd
Changed system type of partition 1 to fd (Linux raid autodetect)

Command (m for help): <-- t
Partition number (1-4): <-- 2
Hex code (type L to list codes): <-- fd
Changed system type of partition 2 to fd (Linux raid autodetect)

Command (m for help): <-- t
Partition number (1-4): <-- 3
Hex code (type L to list codes): <-- fd
Changed system type of partition 3 to fd (Linux raid autodetect)

Command (m for help): <-- w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.
[root@server1 ~]#

Now we can add /dev/sda1, /dev/sda2, and /dev/sda3 to the respective RAID arrays:

mdadm --add /dev/md0 /dev/sda1
mdadm --add /dev/md1 /dev/sda2
mdadm --add /dev/md2 /dev/sda3

Now take a look at

cat /proc/mdstat

... and you should see that the RAID arrays are being synchronized:

[root@server1 ~]# cat /proc/mdstat
Personalities : [raid1] [raid6] [raid5] [raid4]
md0 : active raid1 sda1[0] sdb1[1]
      104320 blocks [2/2] [UU]

md1 : active raid1 sda2[0] sdb2[1]
      513984 blocks [2/2] [UU]

md2 : active raid1 sda3[2] sdb3[1]
      4618560 blocks [2/1] [_U]
      [=====>...............]  recovery = 29.9% (1384256/4618560) finish=2.3min speed=22626K/sec

unused devices: <none>
[root@server1 ~]#

(You can run

watch cat /proc/mdstat

to get an ongoing output of the process. To leave watch, press CTRL+C.)

Wait until the synchronization has finished (the output should then look like this:

[root@server1 ~]# cat /proc/mdstat
Personalities : [raid1] [raid6] [raid5] [raid4]
md0 : active raid1 sda1[0] sdb1[1]
      104320 blocks [2/2] [UU]

md1 : active raid1 sda2[0] sdb2[1]
      513984 blocks [2/2] [UU]

md2 : active raid1 sda3[0] sdb3[1]
      4618560 blocks [2/2] [UU]

unused devices: <none>
[root@server1 ~]#

).

Then adjust /etc/mdadm.conf to the new situation:

mdadm --examine --scan > /etc/mdadm.conf

/etc/mdadm.conf should now look something like this:

cat /etc/mdadm.conf

ARRAY /dev/md0 level=raid1 num-devices=2 UUID=2848a3f5:cd1c26b6:e762ed83:696752f9
ARRAY /dev/md1 level=raid1 num-devices=2 UUID=8a004bac:92261691:227767de:4adf6592
ARRAY /dev/md2 level=raid1 num-devices=2 UUID=939f1c71:be9c10fd:d9e5f8c6:a46bcd49

 

8 Preparing GRUB (Part 2)

We are almost done now. Now we must modify /boot/grub/menu.lst again. Right now it is configured to boot from /dev/sdb (hd1,0). Of course, we still want the system to be able to boot in case /dev/sdb fails. Therefore we copy the first kernel stanza (which contains hd1), paste it below and replace hd1 with hd0. Furthermore we comment out all other kernel stanzas so that it looks as follows:

vi /boot/grub/menu.lst

# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE:  You have a /boot partition.  This means that
#          all kernel and initrd paths are relative to /boot/, eg.
#          root (hd0,0)
#          kernel /vmlinuz-version ro root=/dev/sda3
#          initrd /initrd-version.img
#boot=/dev/sda
default=0
fallback=1
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title Fedora (2.6.23.1-42.fc8)
        root (hd1,0)
        kernel /vmlinuz-2.6.23.1-42.fc8 ro root=/dev/md2 rhgb quiet
        initrd /initrd-2.6.23.1-42.fc8.img

title Fedora (2.6.23.1-42.fc8)
        root (hd0,0)
        kernel /vmlinuz-2.6.23.1-42.fc8 ro root=/dev/md2 rhgb quiet
        initrd /initrd-2.6.23.1-42.fc8.img

#title Fedora (2.6.23.1-42.fc8)
#       root (hd0,0)
#       kernel /vmlinuz-2.6.23.1-42.fc8 ro root=LABEL=/ rhgb quiet
#       initrd /initrd-2.6.23.1-42.fc8.img

Afterwards, update your ramdisk:

mv /boot/initrd-`uname -r`.img /boot/initrd-`uname -r`.img_orig2
mkinitrd /boot/initrd-`uname -r`.img `uname -r`

... and reboot the system:

reboot

It should boot without problems.

That's it - you've successfully set up software RAID1 on your running Fedora 8 system!


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