====== Mini Raid Software howto ======

===== Prologue =====

  * with the instructions that follow we move a complete root system disk from bare partitions to a RAID 1 software layer.
  * obviously you can use the same trick to upgrade to a RAID 5 software system
  * **all the work is done without putting the server off-line, but it's better to stop the services before starting the copy of the files from the old disk to the new one**
  * only one reboot process is needed if the disks are already installed on the server and if the whole process is correct.

==== The second disk is already installed and the partition Table is empty ====

 **else remove the partitions on the second disk by hand pbefore starting this procedure**

  * /dev/sda: is the original disk from where the system boot
  * /dev/sdb: is the second disk

==== create the correct partitions we need ====
    * 100 MB for the boot partition
    * 2Gbyte for the swap partition (there's no need to put the swap partitions on a raid system)
    * rest of the space disk for the root and others partitions

start fdisk and follow these commands
<code>
 fdisk /dev/sdb
 n
 p
 1
 [enter]
 +100M
 n
 p
 2
 [enter]
 +2048M
 n
 p
 3
 [enter]
 [enter]
 t
 2
 82
 t
 3
 fd
 w
</code>


==== now we need to create the raid 1 partitions for the boot and the other partitions ====
  * /dev/md0 will be the first raid 1 partition used only by the /boot directory
  * /dev/md1 will be the raid 1 disk used for everything else

<code>
 mdadm --create /dev/md0 --level=1 --raid-devices=2 missing /dev/sdb1
 mdadm --create /dev/md1 --level=1 --raid-devices=2 missing /dev/sdb3
 echo 'DEVICE /dev/hd*[0-9] /dev/sd*[0-9]' > /etc/mdadm.conf
 mdadm --detail --scan >> /etc/mdadm.conf
</code>

  * we created the raid devices (in downgraded mode)
  * the informations about the devices is written in the **/etc/mdadm.conf** file.

==== the /dev/md0 partition will be used flat for the boot partitions ====
  * so we can format it right now
<code>
  mkfs.ext3 /dev/md0
</code>

==== the /dev/md1 partition will be splitted using the lvm layer ====
  * if the virtual disk **vg1** is already used, please change the example below
<code>
  pvcreate /dev/md1
  vgcreate vg1 /dev/md1
  lvcreate --name root -L 4G vg1
  lvcreate --name usrlocal -L 4G vg1
  lvcreate --name var -L 4G vg1
  lvcreate --name export -L <bigger than the disk>G vg1
  lvcreate --name export -l <extens available reported by the previous command> vg1
</code>
  * we assigned the /dev/md1 partition to an lvm disk and we created different lvm partitions

  * now we need to format the partitions just created
<code>
  mkfs.ext3 /dev/vg1/root
  mkfs.ext3 /dev/vg1/usr/local
  mkfs.ext3 /dev/vg1/var
  mkfs.ext3 /dev/vg1/export
</code>

==== time to mount the partitions to copy the system from the original disk ====
<code>
  mkdir /1
  mount /dev/vg1/root /1
  cd /1
  mkdir -p boor usr/local var export proc sys dev
  mount /dev/md0 boot
  mount /dev/vg1/usrlocal usr/local
  mount /dev/vg1/var var
  mount /dev/vg1/export export
</code>

  * ok, the new partitions are mounted and ready to receive all the contents
<code>
  rsync -aH --exclude=/1 --exclude=/proc --exclude=/sys --exclude=/dev / /1/
</code>
  * wait until the system is copied
  

==== Create the new initrd image file ====
  * after the copy we need to create a new initrd and change the information in the **/1/etc/fstab** file
  * avoid the use of label inside this file, instead use the physical name of the devices
  * you should have something like that:
<code>
vi /1/etc/fstab

/dev/vg1/root           /                       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/vg1/export         /export                 ext3    defaults        1 2
/dev/vg1/var            /var                    ext3    defaults        1 2
/dev/vg1/usrlocal       /usr/local              ext3    defaults        1 2
#LABEL=SWAP-sda2         swap                    swap    defaults        0 0
LABEL=SWAP-sdb2         swap                    swap    defaults        0 0
</code>
  * the reference to the swap partition on the first disk must be commented

  * now we can create the new initrd image **include also the serial-ata module, if necessary**
<code>
mkinitrd --preload raid1 --preload raid456 --preload sata_nv --fstab /1/etc/fstab /boot/initrd-$(uname -r)-raid.img $(uname -r)
</code>


==== Edit the grub configuration file in the original disk ====
  * change the file adding a instance forthe new disk
  * this is the original instance:
<code>
title Fedora (2.6.23.15-80.fc7) RAID
        root (hd0,0)
        kernel /vmlinuz-2.6.23.15-80.fc7 ro root=/dev/vg1/root vga=791 selinux=0 noipv6 panic=30
        initrd /initrd-2.6.23.15-80.fc7.img
</code>
  * must be changed in:
<code>
title Fedora (2.6.23.15-80.fc7) RAID
        root (hd0,0)
        kernel /vmlinuz-2.6.23.15-80.fc7 ro root=/dev/vg1/root vga=791 selinux=0 noipv6 panic=30
        initrd /initrd-2.6.23.15-80.fc7-2.img

title Fedora (2.6.23.15-80.fc7) RAID
        root (hd1,0)
        kernel /vmlinuz-2.6.23.15-80.fc7 ro root=/dev/vg1/root vga=791 selinux=0 noipv6 panic=30
        initrd /initrd-2.6.23.15-80.fc7-2-raid.img
</code>

  * leave the default boot partition to the old disk, so in case of trouble we can reboot

==== Install the boot loader on the second disk ====
  * we need to install the grub boot loader on the new disk using the **grub** command
  * avoid the **grub-install** command, doesn't work for complex situation like this

<code>
  grub
  root (hd1,0) [enter]
  setup (hd1) [enter]
  quit [enter]
</code>

==== update the data on the second disk ====
 * we need to copy the changes from the original disk to the new one

<code>
  rsync -aH /boot/ /1/boot/
</code>


==== Reboot ====
  * time to reboot and see what happens
<code>
  reboot
</code>

  * **at the boot prompt select the second boot option** and verify that is the right one checking that contains the **root (hd1,0)** line
  * if everything was right the system should boot with the raid 1 disk


===== The New System =====
  * now we have the system running on the software raid disk, but the raid is in downgrade mode (only one disk is operating at the moment)
  * we need to connect the original disk tho the current one
  * for this reason we need to remove all the partitions on the old disk a recreate the new partition map that must be identical to the one of the **/dev/sdb** disk we are using now.

  * in our examples /dev/vg0 is the old lvm disk

==== Deleting the old lvm partitions ====
  * we disable the old lvm partitions to avoid confusion
<code>
 lvchange -a n vg0/root
 lvchange -a n vg0/usrlocal
 lvchange -a n vg0/var
 lvchange -a n vg0/export
</code>

  * now we can erase the lvm partitions
<code>
  lvremove vg0/root
  lvremove vg0/usrlocal
  lvremove vg0/var
  lvremove vg0/export
</code>

  * then we need to remove the vg
<code>
  vgremove vg0
  pvremove /dev/sda3
</code>

==== Creating the new partition table form the second disk ====
 * now we can recreate the new partition table copying the partition of /dev/sdb to /dev/sda
<code>
 sfdisk -d /dev/sdb | sfdisk /dev/sda
</code>
  
==== add the second disk to the raid system ..... ====

<code>
  mdadm --manage /dev/md0 --add /dev/sda1
  mdadm --manage /dev/md1 --add /dev/sda3
</code>
  * the raid subsystem is synchronizing the content of both disks

==== .... and update the grub code ====

<code>
  grub
  root (hd0,0)
  setup (hd0)
  quit
</code>

==== the last task is to create the second swap partition ====

<code>
  mkswap -L SWAP-sda2 /dev/sda2
  swapon /dev/sda2
</code>

  * uncomment the line about the swap partition inside /etc/fstab

===== Kernel upgrade =====
**During Kernel upgrade the grub file must be manually modified in order to add the reference to the second disk**