What best describes the ability to increase the access to server resources and provide fail-safe services by linking two or more discrete computer systems, so they appear to function as though they are one?

Clustering

Explanation:

computer clustering can be regarded as set of connected computers wether

loosely or tightly connected works together and in many aspects they are been visualize as a single system. It should be noted that Clustering is ability to increase the access to server resources and provide fail-safe services by linking two or more discrete computer systems, so they appear to function as though they are one