A company is designing its backup infrastructure and must decide where to store the backed-up dat a. They are considering both on-site and off-site options. Which storage media are commonly used in backup solutions for storing and archiving backup data?

Network Attached Storage (NAS) and Storage Area Network (SAN) arrays are both common systems used as backup targets. NAS provides file-level access over a standard network and is widely used for its simplicity and cost-effectiveness. SAN provides high-performance, block-level access and is common in enterprise environments for demanding backup and recovery operations. Both of these systems predominantly use hard disks (HDDs) as the underlying storage medium. HDDs offer the most favorable balance of high capacity and low cost-per-gigabyte, which is essential for storing the large data volumes typical of backup and long-term archiving.

B. Solid state drives (SSDs) and NVMe drives: Their high cost per gigabyte makes them generally unsuitable for the bulk capacity needs of backup and archiving, where cost-effectiveness is prioritized over high performance.
D. Random Access Memory (RAM) and CPU cache: These are volatile memory types that lose all data when power is removed. They are used for active processing, not for persistent data storage, backup, or archiving.

1. EMC Education Services. (2021). Information Storage and Management (ISM) v4. Wiley.

Chapter 11: Backup and Archive: This chapter details backup architecture, including backup targets. It explicitly mentions, "Disk-based backup provides better RPO and RTO than tape. It can be a NAS, a SAN, or a purpose-built backup appliance." This supports options A and C. The chapter also discusses the cost-effectiveness of different media, implicitly supporting HDDs (E) for capacity.

Chapter 4: Intelligent Storage Systems: This chapter describes the components of storage systems, stating, "HDDs are popular in enterprises for their low cost and high capacity... They are a preferred option for storing data that is not performance-sensitive, such as backups and archives." This directly supports option E.

Chapter 6: Network-Attached Storage (NAS): This chapter describes NAS as a dedicated, high-performance file sharing and storage device, with a common use case being a backup target. This supports option A.

2. Dell Technologies. (2023). Dell PowerProtect DD Series Appliances Datasheet.

The technical specifications for models like the DD9900 and DD6400 list "Usable Capacity" figures ranging from tens of terabytes to petabytes, achieved using high-capacity hard disk drives. This document demonstrates the use of HDDs (E) within a purpose-built backup appliance that functions as a specialized NAS (A).

3. Mellor, C. (2018). Data Storage Networking: Real-World Skills for the CompTIA Storage+ Certification and Beyond. Sybex.

Chapter 7: "Backup and Recovery": This chapter, aligned with industry fundamentals, explains, "The most common backup target today is a disk array, which could be a NAS filer head and its disk shelves or a SAN-attached array." This statement from a reputable technical publication confirms that NAS (A), SAN (C), and the underlying disks (E) are all standard components of modern backup solutions.