You can mount it pretty much wherever you'd like.
Traditionally, permanently-mounted disks (like internal drives) are mounted wherever the stuff they contain would go in the filesystem tree. For example, if you decided to put all of Bob's data on its own disk, you'd mount it at
/home/bob. If you were going to store mail on its own disk, you'd mount it at
/var/mail. Many of the top-level directories can be on their own filesystems.
/var are reasonably common.
DOS and Windows (and Mac OS, too) took a different approach: All file paths start with a (sometimes implicit) drive. The drive something is on is a fundamental part of where a file is (logically) located.
/media is supposed to be used for removable drives, and desktop environments auto-mount stuff there. Sometimes they get confused if you manually put stuff there. So I'd avoid it.
It sounds like you want to mount them under
/home/roger/ somewhere (or whatever your home directory is).
/mnt/ is fine too; its for the system administrator (that'd be you) to decide how to use. You can also create additional directories under
/, that's reasonably common as well.
Are you sure you want multiple filesystems?
If you want to treat multiple disks as one larger disk, you can. This may be what you want. You can do this with either RAID or LVM, though it'll be much harder to use these disks in a dual-boot environment. Your choices are:
- RAID1 (mirror). Will have space of the smaller of the two disks (minus epsilon), but puts the data on both disks. Safeguards against disk failure.
- LVM (spanning, though it can actually do more). Will give additional space (sum of both disk, minus epsilon), but no performance boost. Losing a disk will lose the content on that disk, but the stuff on the other disk may still be recoverable.
- RAID0 (stripe). Will give additional space (sum of both disks, minus epsilon). Potentially doubles both read and write throughput. Loss of either disk will lose all data.
If you have more disks, you have some more choices (RAID5/6 [parity] and RAID10 [combines RAID0 and RAID1]). LVM actually gives you a lot of things besides spanning disks—e.g., you can hot add and remove disks, resize "partitions" (logical volumes), take snapshots, etc. It can be usefully be stacked on top of any of the RAID levels.
Personally, my desktops run LVM over RAID1 or RAID10, and my servers LVM over RAID10 or RAID5/6.