Here's a simple guide - old but still relevant
RAID
Just type something like "RAID array explain" into Google and see what you get.
A proper hardware implementation of RAID 1 at controller level should not stop the OS - the OS requests files from the controller and the controller should serve them from either disk (or just 1 if one fails).
It sounds as if you have software mirroring at Windows level.
Data should not be copied from one disk to the other, rather the data should be written simultaneously to both disks, although in practice there may be slight variations due to the on-disk caches - more accurately the controller sends the data to each disk at the same time (or at least to the buffer for each disk channel). Phew!
HTH