In ZFS it is. Matter-of-fact, best practices for ZFS is to always partition disks, and give the partitions human-intelligible names. Even if ZFS uses the whole disk, in which case just create one large partition.
When using gstripe, I think it is possible; the documentation seems to indicate that the "provider" needs to be a block device, so both a whole disk and a partition should work. Clearly, striping over two partitions on the same disk would be insane for most workloads.
What are you really trying to accomplish? Instead of asking us for technical details, why don't you explain the problem?
