A cold site is a backup facility with little or no hardware equipment installed. A cold site is the most cost-effective option among the three disaster recovery sites. However, due to the fact that a cold site doesn't have any pre-installed equipment, it takes a lot of time to properly set it up so as to fully resume business operations1.
References = 1: Disaster Recovery Sites Comparison: Which one to Choose? - NAKIVO(https://www.nakivo.com/blog/overview-disaster-recovery-sites/)

NIC stands for network interface card, which is a hardware component that allows a server to connect to a network. Configuring NICs in pairs on a server would provide network redundancy, meaning that if one NIC fails, the other one can take over and maintain network connectivity. The other options are not related to network redundancy.

Explanation
A database server is a server that hosts a database management system (DBMS) that stores, organizes, and manipulates data. A database server is suitable for housing customer sales records, as it can provide fast and secure access, query and analysis capabilities, backup and recovery options, and scalability and performance optimization. Some examples of database servers are Microsoft SQL Server, Oracle Database, MySQL, and PostgreSQL. Verified References: [What is a Database Server?]

Reference:
https://blogs.oracle.com/mysql/selinux-and-mysql-v2

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]