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SATA RAID Enclosure w/ Temperature Monitoring?
vanyel asks: "Yesterday, my external USB 2.0 drive enclosure finished cooking a 3/4 full 200G drive after its fan quit working who knows how long ago. In the time honored tradition of closing the barn door *after* the horse has wandered away, I'm accelerating my quest for a RAID solution. In particular, I want something that will support 4 SATA drives and has temperature monitoring that doesn't require a particular vendor's RAID card or Windows. Better yet, is there a RAID-5 NAS that isn't in the $4-5000USD price range. Anyone with a better barn door to close this problem with?"
At least with ATA drives, you can usually use smartd to monitor your drives. This includes temperature and various failure indicators. Usually when a drive fails, there is plenty of warning from small failures that the drive recovers from. When you run smartd, you can receive these warnings.
Here's a clear and concise explanation, with pictures.
With a striped pair of mirrors, a total failure happens only if both drives in one of the mirrors fail; there are two ways this can happen.
With a mirrored pair of stripes, a total failure happens whenever any two drives in different stripes fail; there are four ways this can happen.
In both cases, there are (4 2) = 6 pairs of drives that can fail. Given that two drives have failed, there's a 2/6 = 33% chance that the RAID 1+0 will fail, but a 4/6 = 67% chance that the RAID 0+1 will fail.