"I realize RAID5 is not a real backup solution but it's good as I can get right now"
No it is not, and you understand the larger your disks and array get, the more likely it is that you wont be able to restore from parity anyway..
What exactly is in your 6TB of data that can not be recovered? Calculate the cost of your parity - you needed a raid card?, you for sure needed to buy a disk that gives you enough space to create the parity. For what - you have clearly stated that you understand raid is not a backup. So you have spent money to hope that if a drive fails you an recover the files from the parity - that may not even work. What if 2 disks die? What if your machine catches fire? Your spending money for backup, that is not even a backup What is that not having to restore from backup buy you - a few hours of your time "maybe" down the road for non critical stuff.. Rather spend that money on beer
And what is so critical in 6TB of data? Unless you say home movies/pictures/something you created then I have to disagree on its critical nature in a home setup. I have the complete Star Trek original series in my library - It would suck having to rerip it sure, would take some time. When was the last time I watched one of those? Would I loose anything if went away? No not really other than some point in the future I would pop the disk back into my computer and rip it to my library again.. Because I like to have it there at my fingertips vs having to pull out the disk, etc. Worse case scenario my house burns down.. Oh #### lost my "backup" media of ST-TOS -- what to do what to do.. Oh wait my home owners insurance, I am quite sure they have 100 if not 1000s to buy still. Oh #### look at that new HD version of ST-TOS on BR.. Well screw my old SD copy, now I have better copy and when I get around to it put back in my library, etc. What was the point of spending money for parity again? I just do not see it in the home sorry.. I would love to hear why you feel the money your short on is was best spent on parity for something that if not online 24/7 looses you what?
So should I spend money on parity to save me possible future time that I may or may not even spend?
Now you know what I can not loose - videos and pictures of my grand daughter.. Should I trust that to raid, F no as we clearly all understand raid is not a "backup" So I have copies on multiple disks in my home, I have copies on optical media both local and my son's house that is 30 plus miles away.. You would hope that any sort of natural disaster would not take out both locations.. Now if they drop a nuke on Chicago - both places prob gone, etc.. Lets hope Amazon storage is online still in that worse case scenario The roughly 100GB of actual critical movies and pictures cost me a whole $1 a month on glacier to have my piece of mind and DR.. When it grows to the point that its more cost effective to back it up with some unlimited for price per year service - then will move it there. Either way the money spent on actual backup of my "critical" files I assure you is way less than the cost of your disk for "parity"..
You mention lack of $, well your method I am fairly sure is $ not very well spent in overall safety of your critical files. And that your storing them on RAID without a backup shows that they are not very critical in the first place - so your spending money that buys you nothing but possible loss of some future time in a rerip, redownload, etc. For someone that has lack of $ this seems less than wise