A differential backup is a backup method that protects all the changes that have occurred since the last full backup. A differential backup copies all the files that have been added or modified since the last full backup, regardless of whether they have been backed up before or not. A differential backup does not reset the archive bit of the files, which means they will be backed up again in the next differential backup. A differential backup requires more storage space and time than an incremental backup, but it simplifies the restoration process, as only the last full backup and the last differential backup are needed to restore the data

Grandfather-father-son (GFS) is a common backup rotation scheme that uses daily, weekly, and monthly backup media in a first-in, first-out (FIFO) method. The daily backups are rotated on a 3-months basis using a FIFO system as above. The weekly backups are similarly rotated on a bi-yearly basis, and the monthly backups are rotated on an annual basis. The oldest backup media in each cycle are overwritten by the newest ones. This scheme provides multiple versions of backup data at different intervals, allowing for flexible restoration options. Waterfall is another name for GFS. Synthetic full is a backup method that combines an initial full backup with subsequent incremental backups to create a new full backup without transferring all data again. Tower of Hanoi is another backup rotation scheme that uses an algorithm based on moving disks between three pegs. Reference:
https://en.wikipedia.org/wiki/Backup_rotation_scheme

Explanation
RAID 6 is a type of RAID that uses block-level striping with two parity blocks distributed across all member disks. It allows for two disk failures within the RAID set before any data is lost1. A minimum of four disks is required to create RAID 61. To increase the size of an existing RAID 6 array, the administrator can replace the array drives one at a time with larger drives and then expand the array. This way, the data and parity are rebuilt on each new drive and the array remains operational during the process2.

According to the CompTIA troubleshooting methodology, the fourth step is to establish a plan of action to resolve the problem and implement the solution1. The best practice is to test each solution individually to determine the root cause, rolling back the changes in between each test. This way, the technician can isolate the cause and avoid introducing new problems or making the situation worse. Testing each solution in succession and restoring the server from the latest snapshot (D) is not a good option because it may not identify the root cause and may overwrite important dat a. Implementing the shortest solution first to identify the issue and minimize downtime © is also not a good option because it may not solve the problem or may create new issues. Consulting internet forums to determine which is the most common cause and deploy only that solution (A) is not a good option because it may not apply to the specific situation or may be outdated or inaccurate

Explanation
Link aggregation is a technique that allows multiple network interfaces to act as one logical interface, increasing the bandwidth and redundancy of the connection. This can improve the load balancing of network traffic without requiring any new hardware or software. Round robin, most recently used, and heartbeat are not load balancing methods, but rather scheduling algorithms or monitoring techniques. References: CompTIA Server+ Certification Exam Objectives, Domain 2.0: Networking, Objective 2.3: Given a scenario, configure NIC teaming.