What is the minimum disk requirement for RAID 1?

In RAID 1, which is also known as disk mirroring, the primary requirement is to have at least two disks. The fundamental principle behind RAID 1 is to duplicate the data on one disk onto another, ensuring that there is an exact mirror copy of the data. This redundancy provides data protection; if one disk fails, the system can continue to operate using the other disk without any data loss.

Having only one disk would not fulfill the purpose of RAID 1, as there would be no mirror to provide redundancy. Therefore, a minimum of two disks is required for this configuration to function effectively and provide the benefits of fault tolerance and data integrity. The other options suggest a higher number of disks, which are not necessary for the basic RAID 1 setup, as its core functionality relies solely on two disks.