The optimal backup solution must meet three criteria: cost-effectiveness, granular recovery, and multilocation storage.

1. Multilocation: An off-site or cloud-based storage solution is essential for disaster recovery, satisfying the multilocation requirement by storing data in a geographically separate location from the primary site.

2. Cost-Effective & Granular Recovery: A strategy combining full, incremental, and differential backups provides the most flexibility. Incremental backups are highly cost-effective as they only copy data that has changed since the last backup of any type, minimizing storage space and network bandwidth usage—key cost drivers in the cloud. All three backup types (full, incremental, differential) support the granular recovery of specific files or data points. This combination offers the best balance of recovery speed, storage cost, and data granularity.

B. Cloud site, full, and differential

This option is less cost-effective than a strategy that includes incremental backups, which consume less storage and bandwidth for frequent backups.

C. On-site. full, and incremental

On-site storage fails the multilocation requirement, as it does not protect against a site-wide disaster (e.g., fire, flood) affecting the primary data and its backup.

D. On-site. full, and differential

On-site storage fails the multilocation requirement, offering no protection from localized disasters that could destroy both the original data and the backup.

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1. National Institute of Standards and Technology (NIST) Special Publication 800-34 Rev. 1

Contingency Planning Guide for Federal Information Systems.

Section 3.4.2.1

"Backup Types": This section details full

differential

and incremental backups. It explains that incremental backups copy data modified since the last backup

making them efficient. "Incremental backups are the most efficient because they copy the least amount of data." (Page 29).

Section 3.4.2.2

"Off-site Storage": This section explicitly states

"To protect against a disaster that could damage the primary facility...backup media should be stored at an off-site location." (Page 30). This supports the "multilocation" requirement.

2. Amazon Web Services (AWS) Documentation

How AWS Backup works.

"Backups" section: The documentation explains that AWS Backup leverages the native snapshot capabilities of services like Amazon EBS

which are incremental. "The first snapshot of a volume is always a full snapshot. Subsequent snapshots of the same volume are incremental... This saves on storage costs because data is not duplicated." This directly links the incremental method to the "cost-effective" requirement in a cloud context.

3. Microsoft Azure Documentation

About Azure VM backup.

"Backup process" section: The documentation states

"For Azure VMs

the initial backup is a full backup... Subsequent backups are incremental." This highlights that major cloud providers use incremental backups as a standard

cost-effective practice for virtual machine protection.