Hi
as far as I know you cannot convert a raid1 structure to a raid5 one.
something that can be done , on your own responsability and with all required pre backup job done and check :
- split your RAID1 array
- reinitialize one of your disk superblock (mdadm --zero-superblock /dev/sdxx)
- create a degraded RAID 5 array with the new disk and the one you get from your splitted RAID1 one (saying one disk is missing)
- copy your datas from your RAID1 to your RAID5
- definitely stop your RAID1 array
- reinitialize superblock of this disk
- join last disk to the new RAID5 array
well these are only ideas I am putting there. This is not a HOWTO, and I have never tryied it.
Always think that when something can go wrong it will, so cross check you have correct backup.
G.
PS I found on the net someone with a close approach but creating a degraded RAID5 array on two disks. I didn't knew this can be done ...