[CentOS] Rebuilding Raid 1

Trying a different approch.

Senario

Raid 1 setup Bootable raid drive failed Mirror has been working for almost a month and then rebooted Now can't boot mirror drive grub not mirrored from other drive.

I Fixed bootable drive.

Question?

Can I hook up both drives and boot fixed drive then rebuilt mirror from nonbootable drive to bootable drive?

Does the raid automatically rebuilt when I boot with both drives? Can I run a command to rebuilt from one drive to the other and visa versa

I want to try it but I am worried that if I hook them up and it boots that because the bootable drive has older info it might over write the other drive.

Thanks

Can't seem to figure out how to get the other drive bootable.