Previews refer to files generated while editing to make realtime viewing possible.

Media Cache are files used by Premiere Pro internally.  They're created automatically upon import, and if they ever get deleted, PP will simply recreate them when it needs to.

Both fall under the heading of Scratch, which comes from the term "scratch pad", which is scrap paper to work and take notes with, but not the final draft.

Page file (also called swap file) is hard drive space used by Windows when the available memory has become full.  Windows will write unneeded data in memory to a hard drive so it has room to load the needed data.  With 12GB or more of memory, you probably won't be using the swap very much.  Still, it's a good idea to have it, because Windows can crash if it ever needs it and it's not there.  I know Harm recommend setting the page file manually to a disk other than the C: drive.  I disagree with the idea.  Because the page file isn't used very often in a decent edit system with lots of memory, you're perfectly fine leaving the page file where it is, managed by Windows.  Most people won't see any benefit by tampering with it, and may even mess things up if not done right.

RAID 0 is a bad idea for any edit system.  If one drive fails, you lose all data on both drives.  Here's a better plan:

C: System (Windows and Program installation) - 300GB

D: Project Files (Premiere Pro, After Effects, Encore, etc. as well as any still images and audio files used in the project) - 300GB

E: Media (from the camera) - 1TB

F: Scratch (previews, media cache) - 300GB

G: Export (what comes out of Premiere Pro) - 300GB

I: Archiving (Projects and media, as well as final export) - 2TB network drive

Why is everyone so down on RAID 0?  As far as losing information, if you lose the E drive in your example above, you lose all your media too.

True.  But with one drive, you only worry about that one drive failing.  With a RAID 0, you have to worry about either drive failing.  So the chances of losing the data increase with every drive added to a RAID 0.

As far as speed goes, you won't need it when using most standardized camera formats.  A single modern drive is plenty fast enough for even multiple streams.

Where the speed is really needed is with Uncompressed or 4K formats (like form a RED camera).  But when that speed is needed, I recommend a RAID 3 using an Areca controller card.  It offers most of the speed of a RAID 0, but with built in data security in the event of a drive failure.

Ingesting over HD-SDI or even over the poor man's version, HDMI, requires huge amounts of bandwidth, up to 1.485 Gbps and that is only doable with raid arrays. However JBOD is not advisable and using different disks in a raid0 mens that the size of the smallest disk is all that is used for the array and the rest is not used. In your example mixing 300 and 450 GB disks in an aid0 means that your storage capacity is limited to 4 x 300 GB and is far from optimal because of differences between the two kinds of disks.

For all arrays, stick to the same brand and model for all the member disks.

With HDV you have the compressed tapes with the original footage, albeit in 4:2:0 colorspace, as a backup and thus you can use 2 x 450 aid0 for your media and projects and the other 2 x 300 aid0 for media cache, pagefile and exports. Even then, this may not be enough for uncompressed. I think that with your workflow a dedicated raid controller and a large number of disks in a parity raid is the better solution. Say a setup like:

C: OS & programs

D: 2 x 300 aid0 for pagefile, media cache, previews (sustained transfer rate around 220 MB/s)

E: 5 or 6 x 1000 Raid3/5 for media, projects and export (sustained transfer rate around 330 with 5 to 410 MB/s with 6 drives)

There are some exceptions, but most people, when having finished their project and start exporting think "I'm glad it is finished now. I'll tell my wife/Managing Director/client that it is finished and rendering out to Encore or whatever. I'll grab a beer while I wait for this process to finish to celebrate this milestone."

Remember exporting is the single last step in a project (apart from the authoring in Encore) and happens only once in a project. You may gain a few timeslices by exporting to a different disk if you have one, but if this means you have to reduce your raid to one less disk, the penalty in performance is bigger during the editing phase than the gain during export.

That would speed things up.

But why render out?  Why not use Dynamic Link?