Nas drives / 3TB ? advice

3TB Discs

I've just bought an Icybox enclosure (4 bay) and put two 3TB discs into it as a RAID 0 (Striped) configuration. My hard drives are similar to yours, they are 3TB Seagate Barracuda drives. I needed to reformat the drives to get them to show up as 3TB instead of 2.2TB. I think they show up as 2.2TB when they're formatted as MS-FAT (for windows). Once I'd formatted the drives as Mac OS X (Journaled) they showed up as 6TB (as they are Striped they combine into a big volume).
I bought these drives for use as Time Machine Back-Up drives which (it appears) that they're perfect for. You should have no problems using your disc as a Time Machine back-up drive. I do not use CCC so cannot advise on this.

As for your second question, I think that when you create a RAID set it formats the disc the form the set so yes you would have to start again.

An Icybox isn't the same thing as a real NAS box like the DS213. An Icybox is just an external hard drive enclosure, where as a NAS is a self contained computer running linux, this means that with an Icybox you can choose how to format the drives, ie FAT NTFS etc but with a NAS you're stuck with whatever file system the NAS box uses.

Looking at the Synology website for the model you're interested in shows that it supports drives upto 4TB in size, so you shouldn't have any problems.

I don't know about the DS213, but generally creating a raid array is a destructive process, so if you put data on the drive and then try to create a raid later it may wipe the data in order to do it. You'd have to read the DS213's documentation to check for sure.