Madadm-notes

All the damn details of mdadm that you can never remember when a !@#$!#@ drive dies

• resync
• disks RAID1 array
• examples
• 1 on Ubuntu

Changing partition types

• examples

sfdisk can mirror two disks (usually) so that you can rebuild quickly..

• examples
• boundary issues
• warnings

there are ways to do this as a single command with pipes, but it sucks and does not always create the partitions correctly..

safer way: (Assuming sdb is toast)

1. sfdisk -d /dev/sda > sda.out
2. sfdisk /dev/sdb < sda.out
3. sfdisk -l

Quick and dirty, change drive letter as needed:

• sudo mdadm --create --verbose /dev/md0 --level=1 --raid-devices=2 /dev/sda /dev/sdb
• cat /proc/mdstat (wait until synced)
• sudo mkfs.ext4 -F /dev/md0
• sudo mkdir -p /mnt/md0
• sudo mount /dev/md0 /mnt/md0
• df -h -x devtmpfs -x tmpfs
• sudo mdadm --detail --scan | sudo tee -a /etc/mdadm/mdadm.conf
• sudo update-initramfs -u
• echo '/dev/md0 /mnt/md0 ext4 defaults,nofail,discard 0 0' | sudo tee -a /etc/fstab