MD/RAID notes

Raid Notes

Script

This is a test script for setting up md/raid 10far2

#!/bin/bash
dev1='/dev/sdd'
dev2='/dev/sde'
name='test'
offset='1M'
size='400G'
partnum='1'
parttype='fd00'

if ! [[ $(which sgdisk) =~ (sgdisk) ]]; then
    echo "install gptfdisk package"
    exit 1
fi

echo "prepare ${dev1}"
sgdisk --zapall ${dev1}
echo "sgdisk --mbrtogpt ${dev1}"
sgdisk --mbrtogpt ${dev1}
echo "sgdisk --new ${partnum}:+${offset}:+${size} --typecode ${partnum}:${parttype} --change-name ${partnum}:\"${name}1\" ${dev1}"
sgdisk --new ${partnum}:+${offset}:+${size} --typecode ${partnum}:${parttype} --change-name ${partnum}:${name}1 ${dev1}

echo "prepare ${dev2}"
echo "sgdisk --zapall ${dev2}"
sgdisk --zapall ${dev2}
echo "sgdisk --mbrtogpt ${dev2}"
sgdisk --mbrtogpt ${dev2}
echo "sgdisk --new ${partnum}:+${offset}:+${size} --typecode ${partnum}:${parttype} --change-name ${partnum}:\"${name}2\" ${dev2}"
sgdisk --new ${partnum}:+${offset}:+${size} --typecode ${partnum}:${parttype} --change-name ${partnum}:${name}2 ${dev2}

echo "create md/raid"
mdadm --create --verbose --level=10 --metadata=1.2 --chunk=512 --raid-devices=2 --layout=f2 /dev/md/${name} ${dev1}${partnum} ${dev2}${partnum}

echo "status ..."
cat /proc/mdstat

Note on number of disk in setup

Four disk setup

mdadm --create --verbose --level=10 --metadata=1.2 --chunk=512 --raid-devices=4 --layout=f2 /dev/md/webdata /dev/sda2 /dev/sdb2 /dev/sdc2 /dev/sdd2

Two disk setup

mdadm --create --verbose --level=10 --metadata=1.2 --chunk=512 --raid-devices=2 --layout=f2 /dev/md/${name} /dev/sdc2 /dev/sdd2

To memorize

Status raid building

cat /proc/mdstat

Pipe setup to mdadm.conf

mdadm --detail --scan >> /etc/mdadm.conf

Assembly

mdadm --assemble --scan

Formatting raid

stride = chunk / block
stripe-width = numdisks * stride

Format four disk setup

mkfs.ext4 -v -L ${name} -b 4096 -E stride=128,stripe-width=512 /dev/${name}

Format two disk setup

mkfs.ext4 -v -L ${name} -b 4096 -E stride=128,stripe-width=256 /dev/${name}