Mdadm

mdadm:

	PREPARE DRIVES:
		fdisk /dev/sdb
		n - new
		p - primary partition
		w - write
		(repeat for each drive)
		
	LARGER THAN 2TB PARTITIONS:
		parted /dev/sdb
		mklabel gpt - create GPT partition table instead of msdos
		unit tb - make default units in TB
		mkpart primary 0 3 - create the partition on whole disk (0 3 is 'start' and 'end' in TB)
		print - print partition info

	CREATE RAID:
		mdadm --create --verbose /dev/md0 --level=0 --raid-devices=3 /dev/sdb1 /dev/sdc1 /dev/sdd1 - creates raid-0 on /dev/md0 from the 3 devices
		mdadm -C -v /dev/md0 -l 0 -n 3 /dev/sdb1 /dev/sdc1 /dev/sdd1 - short version

	PARAMETERS:
		--name <name> - give the array a name.
		--force - force the operation. can be used to create a raid with a single drive to recover data.

	SAVE CONFIGURATION:
		mdadm --detail --scan >> /etc/mdadm/mdadm.conf (ubuntu)
		mdadm --detail --scan >> /etc/mdadm.conf (other distributions)
		update-initramfs -u - saves md config to init. (this allows the correct dev name to be used instead of md127)

	CHECKING:
		cat /proc/mdstat
		mdadm --detail /dev/md0 - show details of raid. shows progress of data being rebuilt
		mdadm --monitor --mail=admin@example.com --delay=1800 /dev/md0 - email status (delay in seconds)
		mdadm --examine /dev/sdb1 - examine details of drive
		
	MANAGING:
		mdadm --stop /dev/md0	
		mdadm --assemble /dev/md0 /dev/sdb1 /dev/sdc1 - start raid with these devices
		mdadm --assemble --scan - start all stopped raid
	
	REMOVE RAID:
		umount /dev/md0
		mdadm --stop /dev/md0
		mdadm --zero-superblock /dev/sdb1
		mdadm --zero-superblock /dev/sdc1
		(remember to remove line from fstab)
	
	REMOVE DRIVE:
		umount /dev/md0
		mdadm /dev/md0 --fail /dev/sdc1
		mdadm /dev/md0 --remove /dev/sdc1
		
	REBUILD:
		mdadm /dev/md0 --add /dev/sdd1 - add drive to array. drive must be partitioned just like the original. Data will then be rebuilt.

		
mkfs:
	mkfs -t ext4 -L LABEL /dev/md0 - creates filesystem on raid device