Small size … but Raid 1
Raid 1 is a faut-tolerance configuration known as « disk mirroring ». With Raid 1, data is copied seamlessly and simultaneously, from one disk to another, creating a replica. If one disk gets defected, the other can keep working.
And if by bad luck this should happen to you, you just need to remove the defective disk, replace it with a new one without loss of data.