4 Creating Our RAID Arrays
Now let's create our RAID arrays /dev/md0, /dev/md1, and /dev/md2. /dev/sdb1 will be added to /dev/md0, /dev/sdb2 to /dev/md1, and /dev/sdb3 to /dev/md2. /dev/sda1, /dev/sda2, and /dev/sda3 can't be added right now (because the system is currently running on them), therefore we use the placeholder missing in the following three commands:
mdadm --create /dev/md0 --level=1 --raid-disks=2 missing /dev/sdb1
mdadm --create /dev/md1 --level=1 --raid-disks=2 missing /dev/sdb2
mdadm --create /dev/md2 --level=1 --raid-disks=2 missing /dev/sdb3
The command
cat /proc/mdstat
should now show that you have three degraded RAID arrays ([_U] or [U_] means that an array is degraded while [UU] means that the array is ok):
root@server1:~# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md2 : active raid1 sdb3[1]
4242368 blocks [2/1] [_U]
md1 : active raid1 sdb2[1]
499648 blocks [2/1] [_U]
md0 : active raid1 sdb1[1]
498624 blocks [2/1] [_U]
unused devices: <none>
root@server1:~#
Next we create filesystems on our RAID arrays (ext4 on /dev/md0 and /dev/md2 and swap on /dev/md1):
mkfs.ext4 /dev/md0
mkswap /dev/md1
mkfs.ext4 /dev/md2
Next we must adjust /etc/mdadm/mdadm.conf (which doesn't contain any information about our new RAID arrays yet) to the new situation:
cp /etc/mdadm/mdadm.conf /etc/mdadm/mdadm.conf_orig
mdadm --examine --scan >> /etc/mdadm/mdadm.conf
Display the contents of the file:
cat /etc/mdadm/mdadm.conf
At the bottom of the file you should now see details about our three (degraded) RAID arrays:
# mdadm.conf # # Please refer to mdadm.conf(5) for information about this file. # # by default, scan all partitions (/proc/partitions) for MD superblocks. # alternatively, specify devices to scan, using wildcards if desired. DEVICE partitions # auto-create devices with Debian standard permissions CREATE owner=root group=disk mode=0660 auto=yes # automatically tag new arrays as belonging to the local system HOMEHOST <system> # instruct the monitoring daemon where to send mail alerts MAILADDR root # definitions of existing MD arrays # This file was auto-generated on Mon, 21 Jun 2010 13:21:00 +0200 # by mkconf $Id$ ARRAY /dev/md0 level=raid1 num-devices=2 UUID=68686c40:b924278e:325ecf68:79913751 ARRAY /dev/md1 level=raid1 num-devices=2 UUID=9719181e:3071f655:325ecf68:79913751 ARRAY /dev/md2 level=raid1 num-devices=2 UUID=c3360f0f:7f3d47ec:325ecf68:79913751 |
5 Adjusting The System To RAID1
Now let's mount /dev/md0 and /dev/md2 (we don't need to mount the swap array /dev/md1):
mkdir /mnt/md0
mkdir /mnt/md2
mount /dev/md0 /mnt/md0
mount /dev/md2 /mnt/md2
You should now find both arrays in the output of
mount
root@server1:~# mount
/dev/sda3 on / type ext4 (rw,errors=remount-ro)
proc on /proc type proc (rw,noexec,nosuid,nodev)
none on /sys type sysfs (rw,noexec,nosuid,nodev)
none on /sys/fs/fuse/connections type fusectl (rw)
none on /sys/kernel/debug type debugfs (rw)
none on /sys/kernel/security type securityfs (rw)
none on /dev type devtmpfs (rw,mode=0755)
none on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620)
none on /dev/shm type tmpfs (rw,nosuid,nodev)
none on /var/run type tmpfs (rw,nosuid,mode=0755)
none on /var/lock type tmpfs (rw,noexec,nosuid,nodev)
none on /lib/init/rw type tmpfs (rw,nosuid,mode=0755)
none on /var/lib/ureadahead/debugfs type debugfs (rw,relatime)
/dev/sda1 on /boot type ext4 (rw)
/dev/md0 on /mnt/md0 type ext4 (rw)
/dev/md2 on /mnt/md2 type ext4 (rw)
root@server1:~#
Next we modify /etc/fstab. Comment out the current /, /boot, and swap partitions and add new lines for them where you replace the UUIDs with /dev/md0 (for the /boot partition), /dev/md1 (for the swap partition) and /dev/md2 (for the / partition) so that the file looks as follows:
vi /etc/fstab
# /etc/fstab: static file system information. # # Use 'blkid -o value -s UUID' to print the universally unique identifier # for a device; this may be used with UUID= as a more robust way to name # devices that works even if disks are added and removed. See fstab(5). # # <file system> <mount point> <type> <options> <dump> <pass> proc /proc proc nodev,noexec,nosuid 0 0 # / was on /dev/sda3 during installation #UUID=48d65bba-0f02-44b4-8557-b508309b1963 / ext4 errors=remount-ro 0 1 /dev/md2 / ext4 errors=remount-ro 0 1 # /boot was on /dev/sda1 during installation #UUID=e3a677ee-2db0-4a8a-8d6c-94715c8cd90f /boot ext4 defaults 0 2 /dev/md0 /boot ext4 defaults 0 2 # swap was on /dev/sda2 during installation #UUID=1e27f700-ec54-4de9-9428-c6d47d7921f4 none swap sw 0 0 /dev/md1 none swap sw 0 0 /dev/fd0 /media/floppy0 auto rw,user,noauto,exec,utf8 0 0 |
Next replace /dev/sda1 with /dev/md0 and /dev/sda3 with /dev/md2 in /etc/mtab:
vi /etc/mtab
/dev/md2 / ext4 rw,errors=remount-ro 0 0 proc /proc proc rw,noexec,nosuid,nodev 0 0 none /sys sysfs rw,noexec,nosuid,nodev 0 0 none /sys/fs/fuse/connections fusectl rw 0 0 none /sys/kernel/debug debugfs rw 0 0 none /sys/kernel/security securityfs rw 0 0 none /dev devtmpfs rw,mode=0755 0 0 none /dev/pts devpts rw,noexec,nosuid,gid=5,mode=0620 0 0 none /dev/shm tmpfs rw,nosuid,nodev 0 0 none /var/run tmpfs rw,nosuid,mode=0755 0 0 none /var/lock tmpfs rw,noexec,nosuid,nodev 0 0 none /lib/init/rw tmpfs rw,nosuid,mode=0755 0 0 none /var/lib/ureadahead/debugfs debugfs rw,relatime 0 0 /dev/md0 /boot ext4 rw 0 0 /dev/md0 /mnt/md0 ext4 rw 0 0 /dev/md2 /mnt/md2 ext4 rw 0 0 |
Now up to the GRUB2 boot loader. Create the file /etc/grub.d/09_swraid1_setup as follows:
cp /etc/grub.d/40_custom /etc/grub.d/09_swraid1_setup
vi /etc/grub.d/09_swraid1_setup
#!/bin/sh
exec tail -n +3 $0
# This file provides an easy way to add custom menu entries. Simply type the
# menu entries you want to add after this comment. Be careful not to change
# the 'exec tail' line above.
menuentry 'Ubuntu, with Linux 2.6.32-21-server' --class ubuntu --class gnu-linux --class gnu --class os {
recordfail
insmod raid
insmod mdraid
insmod ext2
set root='(md0)'
linux /vmlinuz-2.6.32-21-server root=/dev/md2 ro quiet
initrd /initrd.img-2.6.32-21-server
}
|
Make sure you use the correct kernel version in the menuentry stanza (in the linux and initrd lines). You can find it out by running
uname -r
or by taking a look at the current menuentry stanzas in the ### BEGIN /etc/grub.d/10_linux ### section in /boot/grub/grub.cfg. Also make sure that you use root=/dev/md2 in the linux line.
The important part in our new menuentry stanza is the line set root='(md0)' - it makes sure that we boot from our RAID1 array /dev/md0 (which will hold the /boot partition) instead of /dev/sda or /dev/sdb which is important if one of our hard drives fails - the system will still be able to boot.
Run
update-grub
to write our new kernel stanza from /etc/grub.d/09_swraid1_setup to /boot/grub/grub.cfg.
Next, we adjust our ramdisk to the new situation:
update-initramfs -u
Now we copy the contents of /dev/sda1 and /dev/sda3 to /dev/md0 and /dev/md2 (which are mounted on /mnt/md0 and /mnt/md2):
cp -dpRx / /mnt/md2
cd /boot
cp -dpRx . /mnt/md0
6 Preparing GRUB2 (Part 1)
Afterwards we must make sure that the GRUB2 bootloader is installed on both hard drives, /dev/sda and /dev/sdb:
grub-install /dev/sda
grub-install /dev/sdb
Now we reboot the system and hope that it boots ok from our RAID arrays:
reboot