Hey Jeremymc7,
I see many of your points and indeed it is about finding the right solution at a comfortable cost like many have expressed along with your self. I know many organizations that has to maintain and protect sensitive information spend a good penny on their infrastructure including but not limited to load balancing, data warehousing and server clustering. For a medium level data protection, RAID 0+1 could provide the redundancies one would look for however when we get far, it's not just about the hard drive but the up time where the switch, cpu, memory, motherboard or power supply failing and for those who have dual hot swap power supply, what if both PSU goes out at the same time. Is there another standby server w/ mirrored data that can go online. I even know companies that have mirrored NOC facilities in a different states in case of natural disasters or is that going to far in ones view. For what we need is simply data protection without the uptime being equal. It is of course plausible to have two things fail at the same time but remote. The way I use my unRaid is to use it as my backup from my laptops and desktops data. These core data files is less than 20GB so pretty easy to have it in a single folder. I do have folders w/ critical data sync up using small apps like the synctoy from MS. So my critical files and folders are copied/sync'd to unRAID so if i loose my desktop copy, i have a back on unRAID. For my laptop, I use a different sync tool that i got off download.com as the SyncToy requires .Net framwork to get installed and didn't want to add that on my laptop. This method works well as it provides a mirror (folder mirrors) of critical data.
I could take it one step further to run another sync on the \\disk1\archive folder to \\disk1\arhcive2 folder if i am in fear of two drives going down at the same time however that would be giving me three mirrors but i'm ok with just having 2 so far. As for the rest of the remaining TB of data is my movies, mp3 and pictures. Oh yes, i do sync up my picture folder on this desktop to unRaid so i can view pictures from my xbmc in the living room.
If I'm using unRaid as my mapped out folder on this desktop then I would have it sync to another disk to have a second backup.
I'm not exactly sure of how much data is critical, maybe mirroring folders could help for you as well?
Good Luck,
M