raid via mdadm - alex-aleyan/linux

https://techjourney.net/create-migrate-existing-working-redhat-centos-system-to-raid-1-raid-10/
https://www.howtoforge.com/set-up-raid1-on-a-running-lvm-system-debian-etch
http://www.ducea.com/2009/03/08/mdadm-cheat-sheet/
https://raid.wiki.kernel.org/index.php/RAID_setup
https://lists.debian.org/debian-user/2015/04/msg00761.html
https://gist.github.com/plepe/52ecc9f18efb32c68d18

Cheat Sheet:

Show current situation:
- mdadm --detail /dev/md? | grep dev
- cat /proc/mdstat
- mdadm --detail --scan
- mdadm --examine --scan
- mdadm --examine /dev/sd??
Create
- mdadm --create --verbose /dev/md0 --level=1 /dev/sda1 /dev/sdb2
Create Config
- mdadm --detail --scan >> /etc/mdadm.conf
Remove drive:
- mdadm /dev/md0 --fail /dev/sda1 --remove /dev/sda1
Add drive:
- mdadm --add /dev/md0 /dev/sdb1
- mdadm --grow --raid-devices=4 /dev/md1 --add /dev/md1 /dev/sdb1 /dev/sdc1

Adding drive:

Reduce the number of raided devices to 1 to prevent the raid synchronization (in case if the drives to be added contained corrupted raid devices).
```
mdadm --grow --raid-devices=1 /dev/md1 --force
```

Check the current situation:

mdadm --examine --scan 
cat /proc/mdstat

Remove RAID for the new disks, just in case the RAID was set up on the “new” disks before:
```
mdadm --stop --scan
mdadm --zero-superblock /dev/sdb{1..9}
```

Change the partition table of disks to MBR with the following commands. Skip this step if your disks do not have GTP partition table.

parted /dev/sdb
(parted) mktable msdos
(parted) quit
Answer Y(es) when prompted with “warning: The existing disk label on /dev/sdb will be destroyed and all data on this disk will be lost. Do you want to continue?”

Linux Convert GTP to MBR

Send update to kernel:
```
partprobe /dev/sdb
```

Partition new drive like raid drive:

sfdisk -d /dev/sda | sfdisk --force /dev/sdb

Set the partition type to Linux Raid Autodetect:

fdisk /dev/sdb

Command (m for help): t
Partition number (1-5): 1
Hex code (type L to list codes): fd
Changed system type of partition 1 to fd (Linux raid autodetect)
Repeat the process for the rest of the partitions on the disk. Then, make the change permanent:

Command (m for help): w
Linux RAID AutoDetect Partition Type

And then send update to kernel:
```
partprobe /dev/sdb
```
Install GRUB onto the drives:
```
GRUB> root (hd0,0)
GRUB> setup (hd0)
```

Add the drives to begin synchronization

mdadm --grow --raid-devices=3 /dev/md1 --add /dev/sdb1 /dev/sdc1

Migrate from RAID /dev/md to NON-RAIDed /dev/sd device:

Launch Rescue DVD.
Zero the Software RAID Super blocks:
```
mdadm --zero-superblock /dev/sdb{1..9}
```
Change the Partition Type from the fd (Active RAID) to the 83 (Linux) for the /dev/sda1 partition and to the 8e (Linux LVM) for the /dev/sda{2..4} partitions.
```
Command (m for help): t
Partition number (1-5): 1
Hex code (type L to list codes): 83
Command (m for help): w
```
Activate the LVMs:
```
vgchange -a y 
```
Run the fsck on the partitions to check the file system integrity:
```
fsck -fy /dev/sda1
fsck -fy /dev/mapper/vg1-*
```
Mount the /dev/mapper/vg1-root at /mnt/root
Change the /boot mount entry in the fstab file from the /dev/md1 device to the /dev/sda1 partition.
```
sed -i -e 's!/dev/md1!/dev/sda1!g' /mnt/root/etc/fstab
```

Shrinking the LVM:

Bring up the LVMs to life:
```
vgchange -a y vg1
```
Mount the /dev/mapper/vg1-root at /mnt/root
Check the current situation with the physical volumes, volume groups, logic volumes, and the file system's sizes/occupation:
```
pvs
vgs
lvs
df -TH
```
Check the integrity of the file system on the LVM we are going to resize:
```
fsck -fy /dev/mapper/vg1-root
```
Unmount the LVMs:
```
umount -l /dev/mapper/vg1*
```
Resize the filesystem on the LVM:
```
resize2fs /dev/mapper/vg1-root 900G
```
Resize the LVM:
```
lvreduce -L 950G /dev/mapper/vg1-root
```
Check the physical volume distribution across the physical partitions to make sure the physical volume to be moved will fit the destination partition:
```
pvs -0+pv_used
```
Move the physical volume to the destination partition:
```
pvmove /dev/sda2 /dev/sda3
```

Remove the source partition from the Volume Group:

vgreduce vg1 /dev/sda2
parted /dev/sda -> rm 2

Optionally, clone the partitions to a new drive:

dd if=/dev/sda1 of=/dev/sdb1 conv=notrunc # for boot partition
To move LVMs from sda2 to sdb2, just add sdb2 to the VG pool, move the PV to sdb2 and remove sdba2

The Rest:

  mdadm --examine --scan
  mdadm --examine --scan >> /etc/mdadm.conf
  mdadm --assemble --scan

  mdadm --examine --scan
  mdadm --detail
  cat /proc/mdstat
  
  watch "mdadm --detail /dev/md? | grep dev"
  watch "cat /proc/mdstat"


UUIDs:
  blkid /dev/md1
  blkid /dev/sda1
  pvdisplay | grep UUID
  vgdisplay | grep UUID
  lvdisplay | grep UUID
  mdadm --examine --scan
  ll /dev/disk/by-uuid/
  

  mdadm --stop --scan
  mdadm --create --verbose /dev/md1 --metadata=0.9 --level=1 --raid-devices=4 missing /dev/sdb1 /dev/sdc1 /dev/sdd1
  mdadm --zero-superblock /dev/sdb{1..9}
  dracut --mdadmconf  --add-drivers "raid1 raid10" --filesystems "ext4 ext3 swap tmpfs devpts sysfs proc" --force 
  /boot/initramfs-$(uname -r).img $(uname -r)

  mdadm --manage /dev/md1 -a /dev/sdb1 
  OR 
  mdadm --add /dev/md1 /dev/sdb1

WARNING: Device mismatch detected for vg/lv which is accessing /dev/sdX# instead of (null):

Remove physical volume:

pvremove /dev/sdX#
vgchange --refresh vg1

FIXME: say something here

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

FIXME: say something here

mdadm --assemble --scan 
cat /proc/mdstat

Reboot

Procedure:

Boot from sda \\
sdb is clone of sda \\
create raid device on sdc \\

  df -h
  fdisk -l

Make sure to begin with the clean start:
  mdadm --examine --scan > /etc/mdadm.conf #should return nothing/empty
  mdadm --assemble --scan
  mdadm --detail --scan
  cat /proc/mdstat

Shutdown all RAID Arrays:
  mdadm --stop --scan

Configure the partition table to MBR (MSDOS):
  parted /dev/sdc
    (parted) mktable msdos
    (parted) quit
  partprobe /dev/sdc

Partition the target HD (sdc) according to the partition layout of the source HD (sdb)
  sfdisk -d /dev/sdb | sfdisk --force /dev/sdc

Using fdisk utility, configure the partition type to be Linux RAID Autodetect:
  fdisk /dev/sdc
    Command (m for help): t
    Partition number (1-5): 1
    Hex code (type L to list codes): fd
    Changed system type of partition 1 to fd (Linux raid autodetect)
    Command (m for help): w

Make sure to remove RAID for the new disks:
  mdadm --stop --scan
  mdadm --zero-superblock /dev/sdc{1..9}

Send the update to KERNEL:
  partprobe /dev/sdc

Load the required modules into the KERNEL:
  modprobe raid1
  cat /proc/mdstat
    Personalities : [raid0] [raid1] [raid10]
    unused devices: <none>

  mdadm --create --verbose /dev/md1 --metadata=0.9 --level=1 --raid-devices=2 missing /dev/sdc1
  mdadm --create --verbose /dev/md2 --metadata=0.9 --level=1 --raid-devices=2 missing /dev/sdc2
  mdadm --create --verbose /dev/md3 --metadata=0.9 --level=1 --raid-devices=2 missing /dev/sdc3
  cat /proc/mdstat
    [raid1]
    md1 : active raid1 sdd1[3]
    4189184 blocks 512K chunks 2 near-copies [4/3] [_UUU]
  
    md2 : active raid1 sdd2[3]
    1939915776 blocks 512K chunks 2 near-copies [4/3] [_UUU]
    bitmap: 15/15 pages [60KB], 65536KB chunk
  
    md3 : active raid1 sdd3[3]
    511936 blocks [4/3] [_UUU]
  
    unused devices: <none>

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

mkfs.ext3 /dev/md1

pvcreate /dev/md2
pvcreate /dev/md3

vgextend vg1 /dev/md2
vgextend vg1 /dev/md3

pvdisplay

vi /etc/fstab
  /dev/md0       /boot           ext3    defaults

vi /etc/mtab
/dev/md0 /boot ext3 rw 0 0

vi /boot/grub/menu.lst
  [...]
  default         0
  fallback        1
  [...]
  <remove> NO rn_NO_DM and rn_NO_MD 

mv /boot/initramfs-$(uname -r).img /boot/initramfs-$(uname -r).img.old
dracut --mdadmconf  --add-drivers "raid1 raid10" --filesystems "ext4 ext3 swap tmpfs devpts sysfs proc" --force /boot/initramfs-$(uname -r).img $(uname -r)

pvmove /dev/sdb2 /dev/md2
pvmove /dev/sdb3 /dev/md3
vgreduce vg1 /dev/sdb2
vgreduce vg1 /dev/sdb3
pvremove /dev/sdb2
pvremove /dev/sdb3
pvdisplay

fdisk /dev/sdb
  Command (m for help): <- t
  Partition number (1-5): <- 5
  Hex code (type L to list codes): <- fd
  Changed system type of partition 5 to fd (Linux raid autodetect)
  Command (m for help): <- w

mdadm --add /dev/md2 /dev/sdb2
mdadm --add /dev/md2 /dev/sdb2
mdadm --add /dev/md3 /dev/sdb3
cat /proc/mdstat
  Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
  md1 : active raid1 sdc1[2] sdb1[1]
        4988032 blocks [2/1] [_U]
        [==>..........]  recovery = 52.5% (2623232/4988032) finish=0.5min speed=74705K/sec
  md2 : active raid1 sdc2[2] sdb2[1]
        4988032 blocks [2/1] [_U]
        [==>..........]  recovery = 52.5% (2623232/4988032) finish=0.5min speed=74705K/sec
  md3 : active raid1 sdc2[2] sdb2[1]
        4988032 blocks [2/1] [_U]
        [==>..........]  recovery = 52.5% (2623232/4988032) finish=0.5min speed=74705K/sec
  
  unused devices: <none>

mount /dev/md0 /mnt/md0
cd /boot
cp -dpRx . /mnt/md0

raid via mdadm - alex-aleyan/linux_wiki GitHub Wiki

Cheat Sheet:

Adding drive:

Migrate from RAID /dev/md to NON-RAIDed /dev/sd device:

Shrinking the LVM:

The Rest:

WARNING: Device mismatch detected for vg/lv which is accessing /dev/sdX# instead of (null):

Procedure:

⚠️ GitHub.com Fallback ⚠️

raid via mdadm - alex-aleyan/linux_wiki GitHub Wiki

Cheat Sheet:

Adding drive:

Migrate from RAID /dev/md to NON-RAIDed /dev/sd device:

Shrinking the LVM:

The Rest:

WARNING: Device mismatch detected for vg/lv which is accessing /dev/sdX# instead of (null):

Procedure:

⚠️ **GitHub.com Fallback** ⚠️

⚠️ GitHub.com Fallback ⚠️