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README.mdadm

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