====== Mdadm ======

=mdadm příkazy=
  mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sd[[ab]]1
  
  mdadm --manage /dev/md0 --fail /dev/sdb3
  
  mdadm --manage /dev/md0 --remove /dev/sdb3

  mdadm --manage /dev/md0 --add /dev/sdc3
  
  echo 'DEVICE /dev/hd*[[0-9]] /dev/sd*[[0-9]]' > mdadm.conf
  
  mdadm --detail --scan >> mdadm.conf
  
  mdadm --grow --bitmap=internal /dev/md0
  
  mdadm --grow --bitmap=none /dev/md0
  
  mdadm --assemble /dev/md3 /dev/sdb3 /dev/sdc3
  
  umount /dev/md0
  
  mdadm --manage /dev/md0 --stop
  
  mdadm --zero-superblock /dev/sdg1
  
  mdadm --create /dev/md0 --chunk=128 --level=raid6 --raid-devices=6 /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1 /dev/sdf1 /dev/sdg1
  
  mdadm --run --readonly /dev/md0
  
  mdadm --examine /dev/sda1
  
  mdadm -S /dev/md0
  
  mdadm --assemble /dev/md0 --force --uuid=a4bd7fc2:b4d40d24:e3edfc41:b9f1a521
  
  You can cancel an array resync in progress using the following sequence of commands (as root):

  echo frozen > /sys/block/md0/md/sync_action
  echo none > /sys/block/md0/md/resync_start
  echo idle > /sys/block/md0/md/sync_action

=3T disk=
  [[root@simlin|~]]# parted /dev/sde
  GNU Parted 1.8.1
  Using /dev/sde
  Welcome to GNU Parted! Type 'help' to view a list of commands.
  (parted) mklabel gpt
  (parted) unit TB
  (parted) mkpart primary 0 3
  (parted) print
  
  Model: ATA WDC WD30EFRX-68A (scsi)
  Disk /dev/sde: 3.00TB
  Sector size (logical/physical): 512B/512B
  Partition Table: gpt
  
  Number  Start   End     Size    File system  Name     Flags
   1      0.00TB  3.00TB  3.00TB               primary
  
  (parted) quit
  Information: Don't forget to update /etc/fstab, if necessary.

=mkfs=
http://busybox.net/~aldot/mkfs_stride.html

  mdadm --create /dev/md1 --level=1 --chunk=1024 --raid-devices=2 /dev/sd[[de]]1
  mkfs.ext3 -b 4096 -E stride=256,stripe-width=256 /dev/md1

=Repair bad blocks=

https://unix.stackexchange.com/questions/42277/linux-repairing-bad-blocks-on-a-raid1-array-with-gpt

You just need to have mdraid scrub the mirror. It'll notice the bad sector, and rewrite it automatically.

  echo 'check' > /sys/block/mdX/md/sync_action    # use 'repair' instead for older kernels

  #!/bin/bash
  
  save="$(tput sc)";
  clear="$(tput rc)$(tput el)";
  for sync in /sys/block/md*/md/sync_action; do
    md="$(echo "$sync" | cut -d/ -f4)"
    cmpl="/sys/block/$md/md/sync_completed"
 
    # check current state and get it repairing.
    read current < "$sync"
    case "$current" in
        idle)
            echo 'repair' > "$sync"
            true
            ;;
        repair)
            echo "WARNING: $md already repairing"
            ;;
        check)
            echo "WARNING: $md checking, aborting check and starting repair"
            echo 'idle' > "$sync"
            echo 'repair' > "$sync"
            ;;
        *)
            echo "ERROR: $md in unknown state $current. ABORT."
            exit 1
            ;;
     esac
 
     echo -n "Repair $md...$save" >&2
     read current < "$sync"
     while [[|"$current" != "idle" ]]; do
         read stat < "$cmpl"
         echo -n "$clear $stat" >&2
         sleep 1
         read current < "$sync"
     done
     echo "$clear done." >&2;
  done
  
  for dev in /dev/sd?; do
     echo "Starting offline data collection for $dev."
     smartctl -t offline "$dev"
  done

=Example=
  [[root@simlin|~]]# cat /proc/mdstat 
  Personalities : [[raid1]] 
  md0 : active raid1 sdb1[[2]] sda1[[1]]
       2930266412 blocks super 1.0 [[2/2]] [UU]
       bitmap: 3/22 pages [[12KB]], 65536KB chunk
  
  unused devices: <none>
  [[root@simlin|~]]# cat /sys/block/md0/md/sync_action
  idle
  [[root@simlin|~]]# echo 'check' > /sys/block/md0/md/sync_action
  [[root@simlin|~]]# cat /sys/block/md0/md/sync_action
  check
  [[root@simlin|~]]# cat /proc/mdstat 
  Personalities : [[raid1]] 
  md0 : active raid1 sdb1[[2]] sda1[[1]]
       2930266412 blocks super 1.0 [[2/2]] [UU]
       [[>....................]]  check =  0.0% (12672/2930266412) finish=42340.2min speed=1152K/sec
       bitmap: 3/22 pages [[12KB]], 65536KB chunk
 
  unused devices: <none>