SSH stands for Secure Shell and it is a network protocol that provides encrypted and authenticated communication between two hosts. SSH can be used to remotely access and administer a server using a command-line interface or a graphical user interface. SSH can ensure the encryption of all server administration traffic, which can prevent eavesdropping, tampering, or spoofing by unauthorized parties.
References: https://www.comptia.org/training/resources/exam-objectives/comptia-server-sk0-005-exam- objectives (Objective 2.4)

Explanation
If the server is not reachable by name but can be accessed by IP address, it means that there is a problem with name resolution. The hosts file and the DNS server are both responsible for mapping hostnames to IP addresses. Therefore, the server administrator should check these two files for any errors or inconsistencies that might prevent the server from being resolved by name. References:
https://www.howtogeek.com/662249/how-to-edit-the-hosts-file-on-linux/
https://www.howtogeek.com/164981/how-to-use-nslookup-to-check-domain-name-information-in-microsoft-win

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 Reference: [Redundant Power Supply Best Practices]

Explanation
The access control methodology that can be described best as allowing a user the least access based on the jobs the user needs to perform is role-based access control (RBAC). RBAC is an access control method that assigns permissions to users based on their roles or functions within an organization. RBAC provides fine-grained and manageable access control by defining what actions each role can perform and what resources each role can access. RBAC follows the principle of least privilege, which means that users are only granted the minimum level of access required to perform their tasks. RBAC can reduce security risks, simplify administration, and enforce compliance policies.

Constant Replication
The primary system replicates data changed data blocks continually. Constant replication is also referred to as "continuous replication." The replication process occurs in the background, permitting users to access the data without interruption.
Constant replication is different than regular backups, where files must be closed to be duplicated.