How To Set Up Software RAID1 On A Running LVM System (Incl. GRUB2 Configuration) (Ubuntu 10.04) - Page 3

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6 Preparing GRUB2

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

7 Preparing /dev/sda

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

df -h

root@server1:~# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/server1-root
                      4.5G  816M  3.4G  19% /
none                  242M  196K  242M   1% /dev
none                  247M     0  247M   0% /dev/shm
none                  247M   40K  247M   1% /var/run
none                  247M     0  247M   0% /var/lock
none                  247M     0  247M   0% /lib/init/rw
/dev/md0              236M   23M  201M  11% /boot
root@server1:~#

The output of

cat /proc/mdstat

should be as follows:

root@server1:~# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md0 : active raid1 sdb1[1]
248768 blocks [2/1] [_U]

md1 : active raid1 sda5[0] sdb5[1]
4990912 blocks [2/2] [UU]

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

The outputs of pvdisplay, vgdisplay, and lvdisplay should be as follows:

pvdisplay

root@server1:~# pvdisplay
  --- Physical volume ---
  PV Name               /dev/md1
  VG Name               server1
  PV Size               4.76 GiB / not usable 1.94 MiB
  Allocatable           yes
  PE Size               4.00 MiB
  Total PE              1218
  Free PE               3
  Allocated PE          1215
  PV UUID               rQf0Rj-Nn9l-VgbP-0kIr-2lve-5jlC-TWTBGp

root@server1:~#

vgdisplay

root@server1:~# vgdisplay
  --- Volume group ---
  VG Name               server1
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  9
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                2
  Open LV               2
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               4.76 GiB
  PE Size               4.00 MiB
  Total PE              1218
  Alloc PE / Size       1215 / 4.75 GiB
  Free  PE / Size       3 / 12.00 MiB
  VG UUID               hMwXAh-zZsA-w39k-g6Bg-LW4W-XX8q-EbyXfA

root@server1:~#

lvdisplay

root@server1:~# lvdisplay
  --- Logical volume ---
  LV Name                /dev/server1/root
  VG Name                server1
  LV UUID                b5A1R5-Zhml-LSNy-v7WY-NVmD-yX1w-tuQVUW
  LV Write Access        read/write
  LV Status              available
  # open                 1
  LV Size                4.49 GiB
  Current LE             1149
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           251:0

  --- Logical volume ---
  LV Name                /dev/server1/swap_1
  VG Name                server1
  LV UUID                2UuF7C-zxKA-Hgz1-gZHe-rFlq-cKW7-jYVCzp
  LV Write Access        read/write
  LV Status              available
  # open                 1
  LV Size                264.00 MiB
  Current LE             66
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           251:1

root@server1:~#

Now we must change the partition type of /dev/sda1 to Linux raid autodetect as well:

fdisk /dev/sda

root@server1:~# fdisk /dev/sda

WARNING: DOS-compatible mode is deprecated. It's strongly recommended to
switch off the mode (command 'c') and change display units to
sectors (command 'u').

Command (m for help): <-- t
Partition number (1-5): <-- 1
Hex code (type L to list codes): <-- fd
Changed system type of partition 1 to fd (Linux raid autodetect)

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

Calling ioctl() to re-read partition table.

WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
Syncing disks.
root@server1:~#

Now we can add /dev/sda1 to the /dev/md0 RAID array:

mdadm --add /dev/md0 /dev/sda1

Now take a look at

cat /proc/mdstat

root@server1:~# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md0 : active raid1 sda1[0] sdb1[1]
248768 blocks [2/2] [UU]

md1 : active raid1 sda5[0] sdb5[1]
4990912 blocks [2/2] [UU]

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

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

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

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

cat /etc/mdadm/mdadm.conf

# 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 Wed, 16 Jun 2010 20:01:25 +0200
# by mkconf $Id$
ARRAY /dev/md0 level=raid1 num-devices=2 UUID=90f05e41:bf936896:325ecf68:79913751
ARRAY /dev/md1 level=raid1 num-devices=2 UUID=1ab36b7f:3e2031c0:325ecf68:79913751

Now we delete /etc/grub.d/09_swraid1_setup...

rm -f /etc/grub.d/09_swraid1_setup

... and update our GRUB2 bootloader configuration:

update-grub
update-initramfs -u

Now if you take a look at /boot/grub/grub.cfg, you should find that the menuentry stanzas in the ### BEGIN /etc/grub.d/10_linux ### section look pretty much the same as what we had in /etc/grub.d/09_swraid1_setup (they should now also be set to boot from /dev/md0 instead of (hd0,1) or (hd1,1)), that's why we don't need /etc/grub.d/09_swraid1_setup anymore.

Reboot the system:

reboot

It should boot without problems.

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