A mirror backup is a type of backup that creates an exact copy of the source data to the destination, without using any compression or encryption. A mirror backup is the best backup scheme to recommend given the need for a shorter restoration time in the event of a disruption, because it allows for the fastest and easiest recovery of data. A mirror backup does not store any previous versions of the files, so it only reflects the current state of the source data. Therefore, a mirror backup requires less storage space than a full backup, but more than an incremental or differential backup.
A differential backup is a type of backup that stores the changes made to the source data since the last full backup. A differential backup requires less storage space and time than a full backup, but more than an incremental backup. However, a differential backup also requires more time and resources to restore than a mirror or full backup, because it needs to combine the last full backup and the latest differential backup to recover the data.
A full backup is a type of backup that copies all the files and folders from the source data to the destination, regardless of whether they have changed or not. A full backup provides the most complete protection of data and the simplest recovery process, but it also requires the most storage space and time to perform. A full backup is usually done periodically, such as weekly or monthly, and followed by incremental or differential backups.
An incremental backup is a type of backup that stores the changes made to the source data since the last backup, whether it was a full or an incremental backup. An incremental backup requires the least storage space and time to perform, but it also requires the most time and resources to restore, because it needs to combine all the previous backups in chronological order to recover the data.

The expected costs for recovering the business would be used when performing a business impact analysis (BIA). A BIA is a process of identifying and evaluating the potential effects ofdisruptions to critical business functions or processes. A BIA helps to determine the recovery priorities, strategies, and resources needed to resume normal operations after a disruption. One of the key outputs of a BIA is an estimate of the financial losses or costs associated with different types of disruptions, such as lost revenue, increased expenses, contractual penalties, or regulatory fines.

The best metric to assure compliance with the policy of providing security awareness training to all new employees is the percentage of new hires that have completed the training, as this directly measures the extent to which the policy is implemented and enforced. The number of new hires who have violated enterprise security policies, the number of reported incidents by new hires, and the percentage of new hires who report incidents are not directly related to the policy, as they may depend on other factors such as the nature and frequency of threats, the effectiveness of security controls, and the reporting culture of the organization. References: CISA Review Manual (Digital Version), Chapter 5, Section 5.7