6 Preparing GRUB

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

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/VolGroup00-LogVol00
                      4.1G  2.0G  1.9G  51% /
/dev/md0              190M   16M  165M   9% /boot
tmpfs                 151M     0  151M   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]
      200704 blocks [2/1] [_U]

md1 : active raid1 sda2[0] sdb2[1]
      5036288 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               VolGroup00
  PV Size               4.80 GB / not usable 22.25 MB
  Allocatable           yes
  PE Size (KByte)       32768
  Total PE              153
  Free PE               1
  Allocated PE          152
  PV UUID               pS3xiy-AEnZ-p3Wf-qY2D-cGus-eyGl-03mWyg

[root@server1 ~]#

vgdisplay

[root@server1 ~]# vgdisplay
  --- Volume group ---
  VG Name               VolGroup00
  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               4.78 GB
  PE Size               32.00 MB
  Total PE              153
  Alloc PE / Size       152 / 4.75 GB
  Free  PE / Size       1 / 32.00 MB
  VG UUID               jJj1DQ-SvKY-6hdr-3MMS-8NOd-pb3l-lS7TA1

[root@server1 ~]#

lvdisplay

[root@server1 ~]# lvdisplay
  --- Logical volume ---
  LV Name                /dev/VolGroup00/LogVol00
  VG Name                VolGroup00
  LV UUID                yt5b4f-m2XC-F3aP-032r-ulAT-Re5P-lmh6hy
  LV Write Access        read/write
  LV Status              available
  # open                 1
  LV Size                4.16 GB
  Current LE             133
  Segments               1
  Allocation             inherit
  Read ahead sectors     0
  Block device           253:0

  --- Logical volume ---
  LV Name                /dev/VolGroup00/LogVol01
  VG Name                VolGroup00
  LV UUID                VrPqpP-40ym-55Gs-ShVm-Hlzs-Jzot-oYnonY
  LV Write Access        read/write
  LV Status              available
  # open                 1
  LV Size                608.00 MB
  Current LE             19
  Segments               1
  Allocation             inherit
  Read ahead sectors     0
  Block device           253:1

[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

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): <- 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.
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 : [raid1] [raid6] [raid5] [raid4]
md0 : active raid1 sda1[0] sdb1[1]
      200704 blocks [2/2] [UU]

md1 : active raid1 sda2[0] sdb2[1]
      5036288 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=7d2bf9c3:7cd9df21:f782dab8:9212d7cb
ARRAY /dev/md1 level=raid1 num-devices=2 UUID=d93a2387:6355b5c5:25ed3e50:2a0e4f96

Reboot the system:

reboot

It should boot without problems.

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