Troubleshooting
===============
 - If re-installed, there is some leftovers from LVM/Device Mapper causing CentOS installer
 to crash (even if 'clearpart' is specified). After first crash, it may be useful.
    * Clean partition tables with
        dd if=/dev/zero of=/dev/<device> bs=512 count=1024
    * Destroy rogue LVM VGs
        vgdestroy <vgname>
    * Destroy rogue device mapper devices
        dmsetup info -C
        dmsetup remove_all
        dmsetup remove <name>
        
  - Sometimes even this does not help. 
    > On CentOS 7.4 mdadm does not recognize the disk, but LVM thinks it is
    part of MD. Then cleaning last megabytes of the former md partition may help.
    > On Fedora 28, mdadm detects the old array and tries to "tear down" it down, but
    fails as raid array is already innactive.
    
    * If raid is still more-or-less healthy. It can be destroyed with
        mdadm --zero-superblock /dev/sdb3
    * Otherwise:
        dd if=/dev/zero of=/dev/sda4 bs=512 seek=$(( $(blockdev --getsz /dev/sda4) - 1024 )) count=1024