The most likely issue that prevents the newly added server from seeing any of the LUNs on the SAN is that a single-mode fiber cable is used in place of multimode. A single-mode fiber cable is a type of optical fiber cable that has a small core diameter and allows only one mode of light to propagate through it. A single-mode fiber cable can transmit data over long distances at high speeds, but it requires more expensive transceivers and connectors than multimode fiber cables. A multimode fiber cable is a type of optical fiber cable that has a larger core diameter and allows multiple modes of light to propagate through it. A multimode fiber cable can transmit data over short distances at lower speeds than single-mode fiber cables, but it is more compatible and cost-effective than single-mode fiber cables. If a single-mode fiber cable is used in place of multimode, it can cause signal loss, attenuation, or mismatch between the devices. References: [CompTIA Server+ Certification Exam Objectives], Domain 3.0: Storage, Objective 3.2: Given a scenario, compare and contrast various storage technologies.

Explanation
A method of application hardening is installing the latest patches. Application hardening is a process of reducing the attack surface and vulnerabilities of an application by applying security measures and best practices. Installing the latest patches is one way to harden an application, as patches are updates that fix bugs, errors, or security issues in an application. By installing the latest patches, an application can be protected from known exploits or threats.
References: CompTIA Server+ SK0-005 Certification Study Guide, Chapter 3, Lesson 3.5, Objective 3.5

Data at rest refers to data that is stored in a persistent state on any device or media, such as hard drives, tapes, or cloud storage. Data at rest does not move for long periods of time unless it is accessed or modified by authorized users or applications. A cold site (A) is a backup location that has minimal or no equipment and resources to resume business operations in case of a disaster. On-site retention is a policy of keeping backup data on premises for a certain period of time before transferring it to an off-site location. Off-site storage (D) is a method of storing backup data in a remote location that is physically or logically separated from the primary site. References: https://docs.microsoft.com/en-us/azure/security/fundamentals/encryption- atrest https://www.techopedia.com/definition/144/cold-site https://www.enterprisestorageforum.com/backup
/onsite-offsite-backup.html https://www.techopedia.com/definition/24195/offsite-storage

Drive encryption is a form of data-at-rest encryption that encrypts the entire hard drive or solid state drive. This means that all the data on the drive, including the operating system, applications, and files, are protected from unauthorized access. Drive encryption is usually implemented at the hardware or firmware level, and requires a password, PIN, or biometric authentication to unlock the drive. Drive encryption is the most comprehensive and secure way to achieve data-at-rest encryption, as it prevents anyone from accessing the data without the proper credentials, even if they physically remove the drive from the server.
References: CompTIA Server+ Study Guide, Chapter 9: Security, page 367.