Raid only a partition

raskion wrote:
I don't think this can be done with the GUI, but I could do via terminal using mdadm.

On a normal linux system you could do this with mdadm. The GUI and NAS software is not designed to support it though. So you'll have trouble setting up shares, etc. I don't suggest it.

raskion wrote:
If this is not possibile, the "backup" solution would be to not use raid at all and duplicate manually the "documents" and "picture" folders. With no raid, I can see the disk as separate or the system will hide details and show me a unique disk like it can be done with LVM?

This will work. You use flexraid, and create two data volumes (one per disk). The share names have to be unique though (documents, backup-documents). Or just create a backup share on the second disk, and create subfolders named documents and picture.

You can also set up backup jobs that will update the backups automatically (on a schedule you set).