Ok, I dont know DSM needs a partition of each drive, this is at installation time, because if you add some drive more after, it uses the same partition when added?
Ok, I think DSM can work with a raid0 or raid1 created on linux, but you tells me that all drives needs to be formatted. I will use the raid1 (only have to backup 100GB of 1TB on the another raid) and i will use this two drives to do some tests. I like this idea to can choose OS as grub/burg in linux to can work with both.
I will let you know the results.
Many thanks!