How is a RAID-1 disk repaired?

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http://serverfault.com – I have a GIGABYTE motherboard GA-P35-DS3 with onboard RAID-1 controller. When I replace one disk, how does the RAID controller detects that there is an empty disk, that has to be filled with the old data? I want to install newer disk with a higher capacity. Can I use a disk image tool like Acronis to copy the disk content from one of the old disks to the new harddisk? Should I write the identical data to both disks? (HowTos)