ML 350 additional SATA RAID controller (mirror only)

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http://serverfault.com – I have a Proliant ML350 G8 with two SAS raid arrays currently set up - thereby maxing the default P420i raid controller. I need to set up a large video dump space in addition to this existing set-up (for non backed up, non-critical, temporary storage). I had planned to just add a 2TB SATA disk and plug it into the motherboard. However I it occurred to me the motherboard might have built-in mirror RAID support? Therefore I could use two SATA disks and have some semblance of redundancy. Is this possible? Or would I need to get a cheap raid card? Any recommendations? (HowTos)