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The explicitly mentioned mdadm so they are not using the "raid" on the cards (anyway, at that price it almost always is software raid implemented in the driver).
With the linux md software raid you can kick off background scans. Read the md(4) man page and linux/Documentation/md.txt for the gory details. There is a lot of good stuff in there.
I love Linux software raid. It has been fast and robust.
A bug in the hand is better than one as yet undetected.