Which of the following is NOT a key component of a firewall appliance?

A key component of a firewall appliance is the processing hardware, which is essential for handling the data packets that flow through the network. This hardware is responsible for executing the firmware and processing the firewall's rules and policies.

Network interfaces are also critical, as they allow the firewall to connect to different network segments and manage traffic effectively between them. They serve as the points of entry and exit for data, ensuring that only authorized traffic is permitted based on the firewall's configurations.

Additionally, software for management and monitoring plays a vital role, as it enables administrators to configure the firewall, set policies, and monitor traffic in real-time. This software is crucial for maintaining the security posture of the network.

In contrast, while backup storage solutions are important for data management and recovery in broader IT infrastructure, they are not considered a key component of a firewall appliance itself. Firewalls primarily focus on traffic management and security rather than data storage, so backup storage does not fall within the core functionality of a firewall appliance.