2. operating-systems
  3. linux
  4. raid-software

    Raid Software (MDx)

    Note: If you've problem like ERROR: sector 0. You could use --force option.

    Global overview (info)

    cat /proc/mdstat

    Detailed information

    mdadm --misc --detail /dev/mdx

    Create a new raid (drives and/or partitions)

    mdadm --create /dev/mdx --level=1 --raid-devices=2 /dev/sdaX /dev/sdbX

    Add a drive to an existing raid

    mdadm /dev/mdx --manage --add /dev/sdbx

    Declare an array as failed

    mdadm --fail /dev/mdx /dev/sdax

    source

    Copy partitions (identical partitions)

    Especially useful if you've changed a drive (e.g. broken), or if you badly manipulate a disk. Let say it happens on /dev/sda:

    # if MBR
sfdisk -d /dev/sdb | sfdisk /dev/sda

# elif GPT (-R for replicate)
sgdisk -R=/dev/sda /dev/sdb

    Remove raid partitions

    umount -l /dev/mdX
mdadm --stop /dev/mdX
mdadm --zero-superblock /dev/sdaX
mdadm --zero-superblock /dev/sdbX ... etc.

    Source

    Resync is pending

    Might happened if you reboot during a sync, the following command will continue the sync:

    mdadm --readwrite /dev/mdx

    source

    Tips

    Add raid on current running system (with root, EFI)

    I was not able to do it, but I keep the process and link in case I try again in future

    Let say you have two disk, on already configured, another with none

    root@ephemeral:~# fdisk -l                                                                                                                                  
Disk /dev/nvme0n1: 894.25 GiB, 960197124096 bytes, 1875385008 sectors
Disk model: SAMSUNG MZQLB960HAJR-00007                                                                                                                      
Units: sectors of 1 * 512 = 512 bytes                                         
Sector size (logical/physical): 512 bytes / 512 bytes       
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt                                                           
Disk identifier: CA6E3FC8-B2C1-8642-AB8D-366D44E0C6C0                                                                                                       
                                                                              
Device               Start        End    Sectors   Size Type  
/dev/nvme0n1p1      262144 1875251199 1874989056 894.1G Linux root (x86-64)
/dev/nvme0n1p2  1875251200 1875382960     131761  64.3M Linux filesystem
/dev/nvme0n1p14       2048       8191       6144     3M BIOS boot
                                                                              
Partition table entries are not in disk order.
                                       
Disk /dev/nvme1n1: 894.25 GiB, 960197124096 bytes, 1875385008 sectors
Disk model: SAMSUNG MZQLB960HAJR-00007               
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

    The whole idea is to:

    1. copy the partition of current running system (nvme0n1) into the empty drive (nvme1n1) (see above section e.g. sgdisk -R=/dev/nvme1n1 /dev/nvmen0n1)
    2. declare the empty drive main partition(s) (nvme1n1p1) as pseudo raid 1, e.g. for one partition mdadm --create --verbose /dev/md0 --force --level=1 --raid-devices=1 /dev/nvme0n1p1
    3. declare the prepared drive as the booted device (fstab edit, update grub, raid type)
    # how to obtain UUID for /dev/md0 ?

# update fstab
/dev/md0 / ext4 rw,discard,errors=remount-ro,x-systemd.growfs 0 1

# Regenerate initrd with mdadm kernel module included
update-initramfs -k all -u
# NOTE I had the following error -> W: Couldn't identify type of root file system for fsck hook  

# update grub (unsure of this step)
# grub-install /dev/nvme1n1p1

# set the future partition as Raid Linux
cfdisk /dev/nvme1n1
    1. copy the data of current running system main partitions into the prepared drive 
    dd if=/dev/nvme0n1p1 of=/dev/nvme1n1p1 bs=1M conv=noerror,sync
dd if=/dev/nvme0n1p2 of=/dev/nvme1n1p2 bs=1M conv=noerror,sync
dd if=/dev/nvme0n1p14 of=/dev/nvme1n1p14 bs=1M conv=noerror,sync
dd if=/dev/nvme0n1p15 of=/dev/nvme1n1p15 bs=1M conv=noerror,sync
    1. reboot, ensure system is working
    2. declare the main partition(s) of previous main disk as raid type (cfdsik /dev/nvme0n1)
    3. now you can add the main partition(s) of previous main disk as part of raid mdadm /dev/md0 --add /dev/nvme0n1p1