How to manually backup an OpenVZ container from command line for Promox

first try to examine the array:

cat /proc/mdstat

examine each of the array:

mdadm --detail /dev/md0

mdadm --detail /dev/md127

Take note of the UUID of each array, they should be the SAME

example: 02068dc1:63b677bb:e3f0cfcc:8ccc0d3b

next, examine the current mdadm scan result:

mdadm --detail --scan

to fix this problem basically we need to do the following:

add the ARRAY line to /etc/mdadm/mdadm.conf then update initrd image to read and include new setting in mdadm.conf, then reboot

nano /etc/mdadm/mdadm.conf 

add this line under the # definitions of existing MD arrays:

ARRAY /dev/md0 UUID=02068dc1:63b677bb:e3f0cfcc:8ccc0d3b

update the initrd image:

update-initramfs -u

reboot

after reboot comes back... examine the array again... you may need to add non-included drives like this:

mdadm --manage /dev/md0 --add /dev/sdb1

monitor rebuilding progress:

cat /proc/mdstat

That is all!