I'm new to RAID and trying to get my head around things. I have owned a Drobo in the past (which I liked) but it failed.

Here's a hypothetical scenario:

Assume I set up a RAID-5 array consisting of four 1TB hot-swappable 2.5" SATA drives. I name this volume 'My Data'. By my calculations, that would give me 2.7TB of usable space and the ability to recover if a single drive fails.

I have a few questions:

1. What happens if I pull out a single 1TB drive and replace it with a 2TB drive? Would the array automatically rebuild itself with no issues? Would the maximum capacity remain 2.7TB?

2. If number (1) above is true and the array rebuilds itself with three 1TB drives one 2TB drive what would happen if I then pulled another 1TB drive out and stuck in a 2TB drive (you can see where I'm going here can't you). Would I eventually be able to gain more storage by gradually adding bigger drives?

From a practical point of view, how much input is required from me as the end user whilst these drives are being pulled out and put in? On the Drobo, the storage space just automagically handles itself. Would I have to be actively involved in telling Ubuntu what was going on or would any of it be automated?

Thanks in advance,