OWC Mercury Elite-AL Pro Qx2
Since January/February, I've been running an OWC Mercury Elite-AL Pro Qx2 with 4 Western Digital 1.5TB Caviar Green drives.
The Caviar Greens are not rated for RAID but they are cheap and easily acquired and have served me well so far.
Until last weekend when one of the drives failed. The drive light began to flash and the audible beep came on. I turned off the beep. Reset the box. It came one again. I pulled out the drive, reset the box and still it refused to go away.
Ordered a new drive, put it in. Rebuild light came on, beep went away, flashing drive light went away.
Sent in the old drive to WD and got a (presumably) new one back. You're advised (by Lloyd Chambers) to always keep a spare in case this stuff happens. You don't want to sit around too long without protection. If a second drive fails, there's a high likelihood of data loss. Then you're SOL.
Then your backup solution comes into play. Do you have a backup of that box? What if you get robbed and someone steals the box AND your backup solution? Yeah, both drives at the same time. Highly likely if they're sitting next to each other as mine are.
Always have an off-site backup even if it's a few weeks old. Rotate through so you are protected against "mayhem" as the Allstate guy would say.
If you're curious just do a search for "Scalable Storage" in the search box to your right.