On my Mac Pro, I have a 500gb 7200 Hybrid Drive with System and Application files and nothing else. I have a CalDigit Raid card and an HD Element 4x1.5 external raid in RAID 0. The CalDigit raid card is also raiding (in RAID 5) the 4 internal bays with 8 TBs. The Internal raid is my Time-Machine volume and the external RAID is my Media RAID. This way, if my Mac Pro goes down, I can move it to my other MacPro which also has a CalDigit Raid card. Because the Time Machine volume is on a really fast RAID, I never have any slowdown on hourly backups.
When I'm editing, I usually version up at least once a day or when there's a major structural change to the edit. The only way I know to version up is to dupe your Project (but not the Event) and put the old version in a folder to get them out of the way.
When the job's over, I archive everything off my system by copying everything from the Events folder to an Events archive on a 1TB drive and copying the Projects to a Projects archive on the same external drive (I use bare drives in a drive dock). I then dupe this HD to another drive and take it off site. If I have to get back to the project, I restore the Project folders and Event folders to my main media drive and everything seems to work just fine.
What I'm finding interesting, especially in the new age of Thunderbolt, is that it's really not that important to have massive internal drives anymore and just have a drive big enough for programs and system. That's why having a 248 gb SSD is no longer a drag. Keep all your media off you main drive and have the rest on portable/removable drives!