# ---
# - Speedup rebuilding and re-syncing linux software raid
# ---

## -    http://www.cyberciti.biz/tips/linux-raid-increase-resync-rebuild-speed.html
## -
echo 200000 > /proc/sys/dev/raid/speed_limit_max
echo 200000 > /proc/sys/dev/raid/speed_limit_min


## - swap device /dev/md0 (auto.read-only)
## -
swapoff -a
mkswap /dev/md0
swapon -a


# ---
# - (Re)activate inactiv array /dev/md0
# ---

mdadm --manage /dev/md0 --run


# ---
# - Completely removing a mdadm raid array
# ---

## - # cat /proc/mdstat
## -    Personalities : [raid1] [raid6] [raid5] [raid4] [linear] [multipath] [raid0] [raid10]
## -    md1 : active raid1 sda3[0] sdb3[1]
## -          80533504 blocks super 1.2 [2/2] [UU]
## -    ...
## -

# - See details
# -
mdadm --detail /dev/md1

# - Unmount raid array if mounted
# -
umount /dev/md1

# - Completly remove /dev/md2
# -
mdadm --stop /dev/md1
mdadm --remove /dev/md1


# - zero the superblock FOR EACH drive
# -
mdadm --zero-superblock /dev/sda3
mdadm --zero-superblock /dev/sda6

# - Make the changes known to initramfs
# -
update-initramfs -u -k all


# ---
# - Create an array with ONLY 1 DEVICE
# ---

## - This can be useful, if having a harddisk previosly configured/used
## - in a raid 1 array.
## -
## - Create raid 1 array with onlx device /dev/sda1
## -
mdadm --create /dev/md0 -l 1 -n 2 /dev/sda1 missing

## - Complte the raid array:
## -
## - Adding device /dev/sb1 into array /dev/md0
## -
mdadm -a /dev/md0 /dev/sdb1


# ---
# - Create an new raid1 array on /dev/sdb1 /dev/sdc1
# ---

mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sd[bc]1

# - write out confile - so the mdadm daemon can read it at startup and
# - mount the devices
# -
cd /tmp
echo 'DEVICE /dev/sdb1 /dev/sdc1'  > mdadm.conf
mdadm --examine --scan --config=mdadm.conf >> mdadm.conf
echo 'MAILADDR ckubu@so36.net'  >> mdadm.conf
cp mdadm.conf /etc/mdadm/mdadm.conf
rm /tmp/mdadm.conf

# - Make the changes known to initramfs
# -
update-initramfs -u -k all

## - !! IMPORTANT !!
## - make sure do format the md device NOT the devices included
## - in the array
## -
## - Notice - Lazy Initialization:
## -
## - For creation of an ext4-filesystem, cleaning up (initializing) inode tables
## - and also initializing journal file are needed. Eanabling lazy
## - initialization speeds up the creation, and do that after mounting first
## - time. This is enabled by default.
## -
## - to disable lazy initialation use:
## -
## -    mkfs.ext4 -E lazy_itable_init=0,lazy_journal_init=0 /dev/md0
## -
## - Die "-m" Option reserviert soviel Prozent (hier: 0 Prozent) des Speichers
## - für den Superuser. Vergisst man die Option anzugeben, werden standardmäßig 5%
## - des Speicherplatzers für den Superuser reserviert.
## -
mkfs.ext4 -m0 -E lazy_itable_init=0,lazy_journal_init=0 /dev/md0
mkfs.ext4 -E lazy_itable_init=0,lazy_journal_init=0 /dev/md0

mkfs.ext4 /dev/md0


# ---
# - Verschiedene 'mdadm' Operationen..
# ---

## - stop md device /dev/md0
## -
mdadm --stop /dev/md0

## - start md device /dev/md0
## -
## -    -A  =  --assemble
## -    -s  =  --scan
## -
mdadm -As /dev/md0

## - als defekt markieren. Damit stoppt die Verwendung:
## -
mdadm -f <md-device> <partition-device>

## - remove device fom raid-array
## -
mdadm -r <md-device> <partition-device>

## - (re)add device to raid-array
## -
mdadm -a <md-device> <partition-device>

## - Raid Array ist im auto-read-only status
## -
## - Ändern durch:
## -
mdadm --readwrite /dev/md<n>

## - send a testmessage
## -
mdadm --monitor --test -1 --scan
## - or just for one md-array
## -
mdadm --monitor --test -1 </dev/md?>


## - Print detail
## -
mdadm -D </dev/md?>



# =====
# - MBR-Partitionstabelle sichern und wiederherstellen
# =====

## - Save partitiontable
## -
sfdisk -d /dev/sdb > partitions.sdb.txt

## - Restore partitiontable
## -
cat partitions.sdb.txt | sfdisk /dev/sdb

## - oder
## -
sfdisk /dev/sdb < partitions.sdb.txt


# =====
# - Restore (replicate) partition table on /dev/sdb (defet device) from /dev/sda (undemaged device)
# =====

## - Replicate GPT partition scheme from /dev/sda to /dev/sdd (useful for RAID array rebuild)
## -
## -    !! Faulty device: /dev/sdb !!
## -
sfdisk -d /dev/sda | sfdisk /dev/sdb

## - oder (force)
## -
sfdisk -d /dev/sda | sfdisk -f /dev/sdb
                               ^^^^^^^^
                               faulty device



# =====
# - GPT Partitionstabelle sichern und wiederherstellen
# =====

## - Save partitiontable
## -
## -    sgdisk --backup={/path/to/file} {/dev/device/here}
## -
sgdisk --backup=/root/partitions.sdg.txt /dev/sdg


## - Restore partitiontable
## -
## -    sgdisk --load-backup={/path/to/file} {/dev/device/here}
## -
sgdisk --load-backup=/root/partitions.sdg.txt /dev/sdg


# =====
# - Restore (replicate) partition table on /dev/sdg (defet device) from /dev/sdd (undemaged device)
# =====

## - Replicate GPT partition scheme from /dev/sda to /dev/sdd (useful for RAID array rebuild)
## -
## -    !! Faulty device: /dev/sdg !!
## -
sgdisk -R /dev/sdg /dev/sdd
          ^^
          faulty device

## - Anschließend neue zufällig GUID vergeben
## -
sgdisk -G /dev/sdd