Hiya bud.
Having run a few different types of Matrix Raid now, and also run Windows Home Server... I would recommend having a bit of a read about the latter.
I know nothing about Linux and didn't really find the sort of 'file-serving' function in any of the XP/Vista/W7 builds I did, so looked at WHS, and now recommend it for both backing up and media serving in a home network environment. As an aside... it actually makes a lot of sense in some small business situations as you can do bare-metal rebuilds from the backups on the WHS.
In short... it will take any drives you give it and simply bundle them all up together as a storage drive. Within that, you can tell it to store everything in two places, so that if a drive fails, it's still safe in another place. You can also do that with the media that you have in place to share across the network.
I've been running one for several months now and really like it. I'm still learning the 'best' way to have everything, but it is pretty straightforward. I still have backed up individual users data to their own folders, but in reality, it could all simply be on their main PC's and backed up in the usual WHS manner... I just wanted a good start-point of having all the data saved in one central place.
On the other hand... if you do want to set things up using another O/S in a matrix array... I'd be seriously thinking about running a Raid5/Raid5 setup, as O/S speed will not be an issue for what you are doing. That way, if a drive drops its breakfast, the others simply carry on until you replace the stuffed drive, rebuild the new one when introduced (automatically) and carry on. Raid0/Raid5 on the other hand will simply not work when a drive does that, and rebuilding your Raid0 part will potentially give you a bit of grief, and leave your system down until the drive gets replaced and the Raid0 part rebuilt.
If you still want the questions you've listed answered... come back with them again, but in short...
1. If your Raid5 drops a drive, simply replacing the troubled drive as I said, is really simple... the O/S takes care of it all by itself.
2. You want the O/S part slightly larger than you need, as changing it later could cause you some grief (another advantage of WHS... it just takes whatever it needs).
3. O/S... I believe WHS to be the simplest and best for the role you've described, and haven't found other MS O/S's to do the job as well.
4. This is where you do need to experiment a bit with the Matrix... in general, defaults work jst fine, but for those using mainly large files (so not MP3's or the like) then larger sizes can provide a slight advantage in speed.
Hope that helps put you on the right path... "Which pill will you choose?" comes to mind.
Hey mate thanks for getting back to me.
I've definately thought about WHS, though I probably need to do a little more research.
Correct me if I'm wrong but I believe WHS works via software raid?
I guess the main reason I was thinking Matrix Raid is because I'm planning this build to be quite portable, so I can take it with me when I have a Lan with mates etc.. and I can get really quick read/write speeds when sharing movies etc..
So could I still set up a matrix raid then use WHS as my OS or will this not work?
Cheers
Sam