ChromeTusk :
I have an Asus M4A89GTDPro/USB3 motherboard. The AMD 890XG/SB850 chipset supports RAID 0, 1, 5, and 1+0. The board also has 6 internal SATA3 (6.0Gb/s) ports and 1 eSATA on the rear panel. I will likely use a 4-drive array with 1-2 optical drives.
Regarding backups, I do not do them often enough so the RAID is an added layer for reliability in-between the backups. My wife lost a lot of work on one of her laptops so I ask her to back up the files onto my PC.
About backups, this RAID is a legitimate backup for your wife's files since it's a copy that is not on her primary storage.
The motherboard will give you good enough RAID performance unless you want to do high-throughput stuff like video editing, which seems not to be the case. RAID in the BIOS, not in the OS. OS RAID works, but is slower and eats resources.
If your SATA ports are currently set to IDE mode, you will have to prep the OS and change the mode to RAID. Depending on the OS, changing from AHCI to RAID may be a non-issue. How to do this change depends on your OS; it is easier for Win7. Did you mention your OS? I don't recall seeing it.
Another obligatory (?) warning: If the controller fails, you will likely need a compatible / identical controller (same mobo if you do it in BIOS) to recover. RAID formats are not sufficiently standardized (?) that you can take a RAID0 off one controller and run it on another. A member wrote a guide that may help with doing this (should it prove necessary) :
http://www.tomshardware.com/forum/196922-32-switching-storage-controllers-reinstalling-windows .
Having a RAID with redundancy (0+1, 5, 6) will indeed reduce your chance of loss of data due to spindle failure, but it will increase your risk of data loss due to other factors. A failed controller, for example. Data recovery from a failed RAID array is much harder than from a single drive.
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Personal style note: I am paranoid about doing backups, but still do not do them often enough to meet my own standards. I compensate for this by mirroring key directories, in which I would not like to lose even a day's activity, to a partition on a second drive using Mirror Folder. Addressing reliability (uptime) and data protection (backup) are intertwined but distinct issues. For example, my "online backups" are vulnerable to a power surge or to malware. You need to set your priorities and accept the remaining risks.