raid 4 3 disks + 2 parity disks

Question

I have a raid 0 with 3 disks and I want to be able to lose some disks without losing data. I'm using mdadm and I already started to grow my config

Current config:

Personalities : [raid0] [linear] [multipath] [raid1] [raid6] [raid5] [raid4] [raid10] 
md0 : active raid0 sdd[2] sdb[1] sda[0]
      46877242368 blocks super 1.2 512k chunks
      
unused devices: <none>

Command used to grow:

mdadm --grow /dev/md0 --raid-devices=5 --add /dev/sdc /dev/sde

In the end, will I have 2 parity disks? Or it's impossible and I need to back up my data and start with raid 6 from the beginning? Otherwise is it possible to use raid 1 (2 disks) for the parity disk of the raid 4? (for having the same security as raid 6)

Thanks in advance for your help.

Answer 1

I think the command is mostly correct but incomplete – you specifically need to tell mdadm to change the RAID profile, using the --level=6 option (RAID 6). This will reshape the array, and mdadm supports converting between various different RAID formats, including 0→5 and 0→6.

However, always keep backups, in case something goes wrong during reshaping.