Start Parted using
-a optimal to make sure it warns you in case you are creating a partition which is not correctly aligned. Create the partition without specifying any file system using
mkpart primary 1MiB 512MiB
This command creates a 511MiB partition starting at 1MiB and ending at 512MiB.
Use MiB, GiB or TiB when creating the partition. This ensures correct alignment on HDD's with 512B as well as 4096B physical sectors.
1MiB is used as the starting position, as it's the lowest position you can use without Parted complaining about alignment. But make a mental note that sector 40 really is the lowest position with correct alignment, but parted likes 1MiB boundaries and you're wasting very little disk space.
To make the kernel notice the RAID partition and mount it automatically you need to set the raid flag. If your new partition is identified as partition 1 in Parted (check with
p) you set the raid flag using:
set 1 raid on
Verify the partitions sizes with
print, but set
unit display to KiB, MiB, or GiB. If you do not, the default
compact units will show KB, MB and GB.
To sum the answers up:
I know that raid is a possible partition flag, do I have to use it? How is it used by the running system?
No you don't have to. In case you choose not to you have to mount it yourself.
Which file system type should I use? None?
Yes, don't specify one. Parted is moving away from handling file systems, the stuff relating to filesystems at the moment should be avoided.