Oh, I didn't realise you were using the hardware RAID card for this. In that case, yes, that makes sense, you won't see the other partitions because they're handled by the RAID card. I admit I'd never tried it with a RAID 1 mirror where you might expect to - I've only used RAID 5 on the hardware cards where there's no expectation, of course, to pull a drive to relocate the data.
So you may ask why not just use a single partition for my RAID1 design. The reason is that I prefer to partition HDD because it is good for HDD lifespan. I don't like to design my parition schema to be just a single big parition with 1T Hard Drive since all data are going to be stored scattered and hence, taking longer for spindle reading.
I don't agree with most of this statement. I've not seen anything that indicates partitioning improves lifespan - for any given data, the disk spins the exact same number of times, and the heads move the same number of times, regardless of the partitioning - partitioning is only a logical, not a physical, construct.
As for the data being scattered and spindle latency, that's nowhere near the problem it used to be in the past thanks to faster spindles and larger caches. In addition, Mac OS X uses a dynamic reallocation/fragmentation system that automatically (re)allocates files as they're used, meaning you don't have the level of fragmentation that you used to have.
The primary benefit of partitioning is to restrict file system sizes so that you don't get a runaway proceess filling up the entire disk. Even that is less of a problem - when an 8GB drive was large it didn't take much to fill it, but you'd have to have a pretty rampant process to fill up a 1TB drive before alarms started ringing.
