Explanation
The tool that the administrator should use to check for unnecessary running services across 12 servers is a port scanner. A port scanner is a tool that scans a network device for open ports and identifies the services or applications that are running on those ports. A port scanner can help detect any unauthorized or unwanted services that may pose a security risk or consume network resources. A port scanner can also help troubleshoot network connectivity issues or verify firewall rules.

RTO (Recovery Time Objective) is a measure of how much downtime an organization can tolerate during an unplanned outage. It is the maximum time allowed for restoring normal operations after a disaster. RTO is one of the key metrics for disaster recovery planning and testing. SLA (Service Level Agreement) is a contract that defines the expected level of service and performance between a provider and a customer. BIA (Business Impact Analysis) is a process that identifies and evaluates the potential effects of a disaster on critical business functions and processes. MTTR (Mean Time To Repair) is a measure of how long it takes to fix a failed component or system. Reference: https://parachute.cloud/rto-vs-rpo/ https://www.techopedia.com/definition/13622/service-level-agreement-sla https://www.techopedia.com/definition/1032/business-impact-analysis-bia https://www.techopedia.com/definition/8239/mean-time-to-repair-mttr

The next thing that the technician should do, given the disk is hot swappable, is to replace the disk. A hot swappable disk is a disk that can be removed and replaced without shutting down the system or affecting its operation. A hot swappable disk is typically used in a storage array that has RAID (Redundant Array of Independent Disks) configuration that provides fault tolerance and redundancy. If a disk fails in a RAID array, it can be replaced by a new disk without interrupting the service or losing any data. The new disk will automatically rebuild itself using the data from the other disks in the array.

These are some steps for resolving issues with DNS. A gateway is not required for LAN access so this cannot be the answer.
Solution 1: Check your Computer is correct or not for IP Address
Solution 2: Flush and Reset a client resolver cache and Renew DNS client registration Solution 3: Edit DNS Lookup Host file entry
https://morgantechspace.com/2014/03/can-ping-by-ip-address-but-not-by-machine-name.html#

Port 22 is used for SSH (Secure Shell), which is a secure and encrypted protocol for remote access to a server. Port 23 is used for Telnet, which is an insecure and unencrypted protocol for remote access. Port 990 is used for FTPS (File Transfer Protocol Secure), which is a secure and encrypted protocol for file transfer. The administrator should open port 22 and close port 23 to enable SSH and disable Telnet, as SSH is more secure and reliable than Telnet. The administrator does not need to open port 990, as FTPS is not required for making configuration changes123.
References = 1: Remote Desktop - Allow access to your PC from outside your network(https://learn.microsoft.com/en-us/windows-server/remote/remote-desktop-services/clients/remote-desktop-allow-outside-access) 2: Test remote network port connection in Windows 10 - Winaero(https://winaero.com/test-remote-network-port-connection-in-windows-10/) 3: Windows Command to check if a remote server port is opened?(https://superuser.com/questions/1035018/windows-command-to-check-if-a-remote-server-port-is-opened)