Re-configuring a Raid array from Raid 1 to a Raid 10 with room for expansion.

Hi All,

So here is my scenario, I current have a T320 power edge tower with 8-3.5 hot swap bays with 2 bays with 1 Tb hard drives configured in a Raid 1 configuration. What I want to do is add 4 - 1 Tb hard drive to my server and reconfigure to a raid 10. So now I still have 2 empty drive bays that I will be expending to at some time in the near future. So I have a couple of questions as this is my first server. Would like to set this up the right way so that when I add those last 2 hard drive that I don't have to Back up, Wipe, Reconfigure, Re-install as it was explained to me. So here are my questions:

1. Can I configure my Raid 10 at this point with 4 - 1 Tb drives with 2 hot spare drives with and eye on the future to add 2 additional 1 Tb drives to the raid 10 for a total of 3 sets of raid 10 drives with 2 hot spares waiting in the wings for failover?

2. If I configure my server in this fashion will I be able to just add the 2 additional drives later without any reconfiguration or loss of data?

3. if I can't use raid 10 in this fashion what raid can I use instead?

4.In the future will I be able to swap my 1 Tb drives for larger Tb drives in order to increase on overall storage capacity without reconfiguration or loss of data?

5. I have been wrestling with how to have a external back up system.The 1 major stumbling block I keep coming across is that by my calculation I'll end up with about 12 Tb's of storage if I use 4 Tb capacity hard drives, So how and what do you back that amount data up on externally and keep off premise?

Any help that can be offer in this matter would be greatly appreciated,

Thanks