Explanation:
Resiliency levels
To create a highly available virtual disk, you need at least one physical disk that satisfies the following requirements:
1.One physical disk is required to create a storage pool.
2.A minimum of two physical disks are required to create a resilient mirror virtual disk.
3.A minimum of three physical disks are required to create a virtual disk with resiliency through parity.
4.Three-way mirroring requires at least five physical disks.
5.Disks must be blank and unformatted. No volume can exist on the disks.
https://learn.microsoft.com/en-us/training/modules/implement-storage-spaces-storage-spaces- direct/2-define-storage-spaces-architecture-components