[RAID] Adding devices to RAID array using 'mdadm' (Linux)

Owned by Joey Houy (Unlicensed)
Last updated: Nov 17, 2016



Step-by-step guide

  1. Check devices installed using 'fdisk -l'
    You can also use 'df -h' to view list of devices in MB/GB's 

    #Example: 

    root@admin:~$ fdisk -l

        Device   Boot       Start       End           Blocks   Id   System

    /dev/sda1      *               1         20         153600   83   Linux
    /dev/sda2                    20   36990   296960000   83   Linux
    /dev/sda3              36990   52287   122880000   83   Linux
    /dev/sda4              52287   91202   312579072     5   Extended
    /dev/sda5              52288   65036   102400000    83  Linux
    /dev/sda6              65036   66311     10240000    82  Linux swap / Solaris
    /dev/sda7              66311   91202   199936000    83  Linux

     


  2. Check to make sure the device you use is properly partitioned for the RAID array you plan on adding it to
     

  3. Check your current RAID configuration using '/proc/mdstat' to ensure you know which RAID array you are targeting

    root@admin:~$ cat /proc/mdstat
    Personalities : [raid1] [raid6] [raid5] [raid4]
    md1 : active raid1 sdb2[1] sda2[0]
                136448 blocks [2/2] [UU]

    md2 : active raid1 sdb3[1] ada3[0]
                129596288 blocks [2/2] [UU]

    md3 : active raid5 adl1[9] sdk1[8] sdj1[6] sdh1[5] sdg1[4] sdf1[3] sde1[2] sdd[1] sdc[0]
                1318680576 blocks level 5, 1024k chunk, algorithm 2 [10/10] [UUUUUUUUUU]

    md0 : active raid1 sdb[1] sda[0]
                167877736 blocks [2/2] [UU]

    unused devices: <none>
     

  4. Add device to RAID array using 'sudo mdadm --manage /dev/md# --add /dev/sdx#'

    #Example:

    root@admin:~$ sudo mdadm --manage /dev/md1 --add /dev/sda3
     


  5. Check status in '/proc/mdstat'

    #Example:

    Personalities : [raid1] [raid6] [raid5] [raid4]
    md127 : active raid5 sdh1[6] sdg1[4] sdf1[3] sdeq[2] sdd1[1] sdc1[0]
                1464725760 blocks level 5, 64k chunk, algorithm 2 [6/5] [UUUUU_]
                [===>.................]  recovery = 14.2% (41598211/292945152) finish=125.5min speed=33440K/sec