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]
4618560 blocks [2/1] [_U]
md1 : active raid1 sdb2[1]
513984 blocks [2/1] [_U]
md0 : active raid1 sdb1[1]
104320 blocks [2/1] [_U]
unused devices: <none>
[root@server1 ~]#
Next we create filesystems on our RAID arrays (ext3 on /dev/md0 and /dev/md2 and swap on /dev/md1):
mkfs.ext3 /dev/md0
mkswap /dev/md1
mkfs.ext3 /dev/md2
Next we create /etc/mdadm.conf as follows:
mdadm --examine --scan > /etc/mdadm.conf
Display the contents of the file:
cat /etc/mdadm.conf
In the file you should now see details about our three (degraded) RAID arrays:
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 |
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 ext3 (rw)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
/dev/sda1 on /boot type ext3 (rw)
tmpfs on /dev/shm type tmpfs (rw)
none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw)
sunrpc on /var/lib/nfs/rpc_pipefs type rpc_pipefs (rw)
/dev/md0 on /mnt/md0 type ext3 (rw)
/dev/md2 on /mnt/md2 type ext3 (rw)
[root@server1 ~]#
Next we modify /etc/fstab. Replace LABEL=/boot with /dev/md0, LABEL=SWAP-sda2 with /dev/md1, and LABEL=/ with /dev/md2 so that the file looks as follows:
vi /etc/fstab
/dev/md2 / ext3 defaults 1 1 /dev/md0 /boot ext3 defaults 1 2 tmpfs /dev/shm tmpfs defaults 0 0 devpts /dev/pts devpts gid=5,mode=620 0 0 sysfs /sys sysfs defaults 0 0 proc /proc proc defaults 0 0 /dev/md1 swap swap defaults 0 0 |
Next replace LABEL=/boot with /dev/md0 and LABEL=/ with /dev/md2 in /etc/mtab:
vi /etc/mtab
/dev/md2 / ext3 rw 0 0 proc /proc proc rw 0 0 sysfs /sys sysfs rw 0 0 devpts /dev/pts devpts rw,gid=5,mode=620 0 0 /dev/md0 /boot ext3 rw 0 0 tmpfs /dev/shm tmpfs rw 0 0 none /proc/sys/fs/binfmt_misc binfmt_misc rw 0 0 sunrpc /var/lib/nfs/rpc_pipefs rpc_pipefs rw 0 0 |
Now up to the GRUB boot loader. Open /boot/grub/menu.lst and add fallback=1 right after default=0:
vi /boot/grub/menu.lst
[...] default=0 fallback=1 [...] |
This makes that if the first kernel (counting starts with 0, so the first kernel is 0) fails to boot, kernel #2 will be booted.
In the same file, go to the bottom where you should find some kernel stanzas. Copy the first of them and paste the stanza before the first existing stanza; replace root=LABEL=/ with root=/dev/md2 and root (hd0,0) with root (hd1,0):
[...] 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=LABEL=/ rhgb quiet initrd /initrd-2.6.23.1-42.fc8.img |
The whole file should look something like this:
# 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=LABEL=/ rhgb quiet initrd /initrd-2.6.23.1-42.fc8.img |
root (hd1,0) refers to /dev/sdb which is already part of our RAID arrays. We will reboot the system in a few moments; the system will then try to boot from our (still degraded) RAID arrays; if it fails, it will boot from /dev/sda (-> fallback 1).
Next we adjust our ramdisk to the new situation:
mv /boot/initrd-`uname -r`.img /boot/initrd-`uname -r`.img_orig
mkinitrd /boot/initrd-`uname -r`.img `uname -r`
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 GRUB (Part 1)
Afterwards we must install the GRUB bootloader on the second hard drive /dev/sdb:
grub
On the GRUB shell, type in the following commands:
root (hd0,0)
grub> root (hd0,0)
Filesystem type is ext2fs, partition type 0x83
grub>
setup (hd0)
grub> setup (hd0)
Checking if "/boot/grub/stage1" exists... no
Checking if "/grub/stage1" exists... yes
Checking if "/grub/stage2" exists... yes
Checking if "/grub/e2fs_stage1_5" exists... yes
Running "embed /grub/e2fs_stage1_5 (hd0)"... 16 sectors are embedded.
succeeded
Running "install /grub/stage1 (hd0) (hd0)1+16 p (hd0,0)/grub/stage2 /grub/grub.conf"... succeeded
Done.
grub>
root (hd1,0)
grub> root (hd1,0)
Filesystem type is ext2fs, partition type 0xfd
grub>
setup (hd1)
grub> setup (hd1)
Checking if "/boot/grub/stage1" exists... no
Checking if "/grub/stage1" exists... yes
Checking if "/grub/stage2" exists... yes
Checking if "/grub/e2fs_stage1_5" exists... yes
Running "embed /grub/e2fs_stage1_5 (hd1)"... 16 sectors are embedded.
succeeded
Running "install /grub/stage1 (hd1) (hd1)1+16 p (hd1,0)/grub/stage2 /grub/grub.conf"... succeeded
Done.
grub>
quit
Now, back on the normal shell, we reboot the system and hope that it boots ok from our RAID arrays:
reboot