Fdisk fails while creating a raid-1

hello all, I want to create a raid-1-array on my SUSE 8.0 machine. I have built two 10.6 GB raid-partitions on hda(40GB) and hdc(20GB) both in the extended partition of the harddisks. If I tell Yast to create the raid, I get the error that Fdisk failed while creating the raid-array. Is there a possibility to create the raid-array "by hand" (without Yast), and could someone describe me, how to install the raid with alternative Tools. Thanks Kai Pfeiffer