====== Software RAID (MD) ======

==== Desired configuration of the disks ====

^ hdd ^ partition ^ raid1 ^  lvm           ^ mount point ^
| sda |  sda1     |  md0  |  -             | /            |
| sdb |  sdb1     |  md0  |                |              |
| sda |  sda2     |  -    |  -             | swap         |
| sdb |  sdb2     |  -    |                | swap         |
| sdc |  sdc1     |  md1  | vg1            | /home, /srv, |
| sdd |  sdd1     |  md1  | vg1            |   /media     |
| sde |  sde1     |  md2  | vg1            |              |
| sdf |  sdf1     |  md2  | vg1            |              |
| sdg |  sdg1     |  md3  | vg2            | /backup      |
| sdh |  sdh1     |  md3  | vg2            | /backup      |

see also [[deb720:apsys|Hardware configuration]]

==== Replace a failed RAID disk ====

Replace the disk, then copy the partition information from the good disk, randomize the UUID, and re-read the partition information into the system. First, install gdisk from the Debian Universe repositories.

  apt-get install gdisk
  sgdisk -R=/dev/sdb /dev/sda
  sgdisk -G /dev/sdb
  partprobe

Taken from [[http://askubuntu.com/questions/57908/how-can-i-quickly-copy-a-gpt-partition-scheme-from-one-hard-drive-to-another|How can I quickly copy a GPT partition scheme from one hard drive to another?]]

Other resources on [[http://en.wikipedia.org/wiki/Mdadm|mdadm]] and [[http://askubuntu.com/questions/63980/how-do-i-rename-an-mdadm-raid-array|How do I rename an mdadm raid array?]]:
  * https://raid.wiki.kernel.org/index.php/Recovering_a_failed_software_RAID
  * http://en.wikipedia.org/wiki/Mdadm#Creating_an_array
  * https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/4/html/Cluster_Logical_Volume_Manager/VG_activate.html
  * https://raid.wiki.kernel.org/index.php/RAID_Recovery
  * http://www.cyberciti.biz/faq/linux-creating-software-raid-one-arrays/
  * http://www.cyberciti.biz/faq/linux-server-rename-an-mdadm-raid-array/
  * [[https://www.thomas-krenn.com/en/wiki/SMART_tests_with_smartctl|SMART tests with smartctl]]
  * [[http://nwsmith.blogspot.com/2007/08/smartmontools-and-fixing-unreadable.html|Smartmontools and fixing Unreadable Disk Sectors]]
  * [[https://www.backblaze.com/blog/what-smart-stats-indicate-hard-drive-failures/#comment-2938093635|What SMART Stats Tell Us About Hard Drives]]

Setup configuration:
  mdadm -Es >> /etc/mdadm/mdadm.conf


==== Install Base ====

  - Install Ubuntu Hardy (8.04) Alternate Install: F6-F6-Expert Mode
  - Install Raid1 with MD package activated and assign mount points

==== Check wether all volumes get mounted during system boot ====

to check wether root and swap are mounted, enter:
  mount
  free -m -t

to check mismatching uuid's, enter:
  ls -la /dev/disk/by-uuid
  cat /etc/fstab

to fix, do:
  vim /etc/fstab
replace the uuid's found in fstab with the ones found in /dev/disk. Make sure you copy the correct uuid (md0, md1) to the respective entry in fstab.