Table of Contents
RAID 1 and mdadm
This is a “How to” setup for RAID 1 on Linux. It is applied to Debian sarge, however through the use of mdadm (multiple devices admin) it should be able to work on various Linux installs.
RAID 1 setup with a NEW install of Debian Sarge
Two hard disks of 2gb in total each were setup with RAID. This is done through some careful looking in the Debian Install process.
- Make sure also to Choose - linux26 when booting the Debian Install CD
- Follow the install procedure for Creating Partitions VERY carefully.
- The key point is - when creating a volume, do not choose ext3 → choose “RAID Volume” for Both hard disks.
- From the install process it is possible to get the RAID 1 array working perfectly. Note: LVM is NOT used.
General Information on Managing RAID
mdadm is the tool used to control and manage the RAID array. mdadm -D /dev/md0 //Show the details of the md0 array mdadm -E /dev/sda1 //Examine the Hard Disk sda1 cat /proc/mdstat //Shows the RAID array. UU=2 disks are fine. _U=1 disk needsss rebuilding mdadm –examine –scan //Shows the disks and their array. This information should be in the config file /etc/mdadm/mdadm.conf
Monitoring a RAID Array
ps -eaf //It should show the Monitor already! - /sbin/mdadm -F -i /var/run/mdadm.pid -m root -f -s //To monitor manually → mdadm –monitor –mail=root –delay=300 /dev/md0 nohup mdadm –monitor –mail=sysadmin –delay=300 /dev/md0 & //The & will background the monitoring
Prepare BOTH Hard Disks so EITHER one will boot via Grub
This MUST also be DONE after REBUILDING an ARRAY!!! <br> The MBR has to be reinstalled after having replaced the broken disk:
//For Disk 1 grub device (hd0) /dev/sda root (hd0,0) setup (hd0)
//For Disk 2 grub device (hd1) /dev/sdb root (hd1,0) setup (hd1)
How to Rebuild an Array:
mdadm –add /dev/md0 /dev/sda1 mdadm –add /dev/md0 /dev/sdb1 //chose which ever one is necessary //MAKE SURE TO DO THE GRUB BOOT LOADER - OTHERWISE PC WONT BOOT!!!!!!!!!!!
Further Information can be found at: <br> http://www.networknewz.com/2003/0113.html <br> http://www.linuxmanpages.com/man8/mdadm.8.php <br> http://www.planamente.ch/emidio/pages/linux_howto_root_lvm_raid.php#Creating%20RAID%20devices //Excellent <br>