If there are two physically separate hard drives, should they be treated as two pre-defined partitions?

If yes:

• should they be treated as two primary partitions (including one or two of them can become extended partition(s) and be further subdivided into logical partitions)?
• Or they (or one part of each) can be treated as two logical partitions of a extended partition?

Thanks!

I intended to ask if there can be a primary/logical partition that are partially on both hard drives? And if there can be a logical partition on a hard drive and another logical partition on another hard, and the two logical partitions belong to the same extended partition? I guess the answers to both questions are no?