This is the most likely licensing type that will be used because volume licensing allows a single license key to be used for multiple installations of a software product. Volume licensing is typically used by organizations that need to deploy software to a large number of devices or users. Reference: https://www.microsoft.com/en-us/licensing/licensing-programs/volume-licensing-programs

Explanation
The most likely cause of this failure is that both power supplies were connected to the same power feed, which means that they both lost power when utility power was lost. To prevent this from happening, redundant power supplies should be connected to different power feeds, preferably from different sources, such as a UPS or a generator. Verified References: [Redundant Power Supply Best Practices]

An access control vestibule is a physical security concept that limits personnel access to a restricted area within a data center. It is a small room or hallway that has two doors: one that leads to the outside and one that leads to the restricted area. The doors are controlled by an electronic lock that requires authentication, such as a card reader, biometric scanner, or keypad. Only authorized personnel can enter the vestibule and access the restricted area. References: CompTIA Server+ Certification Exam Objectives, Domain 5.0: Security, Objective 5.1: Given a scenario, apply physical security methods to a server.