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Thread: mdadm software raid1 automatic failover

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  1. mdadm software raid1 automatic failover

    Hello experts,

    I have installed SLES 11 SP4 on power using the following scenario

    we have multipathing and we have 2 LUNS
    one LUN is on data center A and one LUN is on data center B

    on each LUN, i made two partitions on install via expert partitioner

    /dev/mapper/LUN1_part1 - 512 MB - ext3 - /boot
    /dev/mapper/LUN1_part2 - 40,5 GB - no fs - not mounted

    /dev/mapper/LUN2_part1 - 512 MB - no fs - not mounted
    /dev/mapper/LUN2_part2 - 40,5 GB - no fs - not mounted

    then I made a software raid1 over mdadm on install time via expert partitioner
    /dev/md0 - on devices /dev/mapper/LUN1_part2 and /dev/mapper/LUN2_part2

    then I created a volume group vg_rootfs on /dev/md0

    then I created the following logical volumes on vg_rootfs
    lv_rootfs - 5 GB - ext3 - /
    lv_home - 5 GB - ext3 - /home
    lv_opt - 5 GB - ext3 - /opt
    lv_usr - 5 GB - ext3 - /usr
    lv_var - 5 GB - ext3 - /var
    lv_tmp - 5 GB - ext3 - /tmp
    lv_var_log - 3 GB - ext3 - /var/log
    lv_swap - 2 GB - swap - swap

    after installation I first wanted to test the failover by taking one LUN away from the system. So far i have NOT replicated the /boot sector via sfdisk to /dev/mapper/LUN2_part1, but I think for this scenario this should not be necessary

    when I take /dev/mapper/LUN1 away from the system (where the /boot sector ist), everything works fine. I can still write files to the file system and i can still do commands in my ssh session. Then I gave the system /dev/mapper/LUN1 back. Now I wanted to test to take away the other LUN and just reboot the system - this is where I fail.

    when I take away /dev/mapper/LUN2, where the /boot sector is currently NOT replicated, ssh freezes and i cannot state any commands.

    How to fix this?

    Best regards
    Last edited by dafrk; 04-Aug-2016 at 15:07.

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