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RAID 1 noob question
(alien.top)
Taking out drives for testing is a no-no unless you're very careful.
If you hook up any drive to Windows it'll write on it and thus your drives aren't the same anymore. If you RAID controller (or software) doesn't catch this you now have an inconsistent RAID config.
What 2 drive case with hardware RAID do you have?
As mentioned, if a drive dies, you just need to take it out and replace with a new one and start RAID rebuild. The vendor should have a guide on this with detailed steps.