That's normal. When you import a foreign configuration, it is almost always going to include a disk that had gone offline first that needs to be rebuilt/synced with the rest of the array.
Hello,  I have a PEdge R710 and RAID 1 config, when i enter CTRL+R i have 5disks in foreign. When I start the OS i cant see any disk, just the first one that has de OS.  What should i do to get the other disk online and then i can see them on the OS. I prefer not to lose data. Thank you
PowerEdge R710