Implement software RAID at running live Linux sever
May I know how to implement software RAID at running live Linux sever.
I saw other site on implementing Software RAID at installation stage, but how about a running Linux ( RHEL v5).
I tried to bring down to level 1 , and do mdadm --create /dev/md0 .
But it failed. I am not able to create md0, 1 , 2 ,3 etc
The type of sda 1,2,3,4 sdb 1,2,3,4 was already fd when i did fdisk ( Option : T )