Reserved resources, or Reserved Instances, are ideal for workloads with predictable usage and a long-term commitment, such as a minimum lifecycle of five years. This model allows for significant cost savings compared to on-demand pricing, and the instance is not ephemeral, meaning it persists and is dedicated to the user for the duration of the reservation. The licensing charged per physical CPU count aligns with dedicated host or reserved instance models, but the long-term commitment points more towards reserved resources.

Block storage provides the greatest performance advantage for traditional relational databases due to its high performance and low-latency characteristics. Block storage allows databases to rapidly manage data in fixed-sized blocks, which is ideal for databases that require frequent read/write operations.References:
Understanding different storage types and their use cases, including block storage for databases, is part of the cloud computing knowledge base covered in CompTIA Cloud+.

Platform as a Service (PaaS) provides a platform allowing customers to develop, run, and manage applications without the complexity of building and maintaining the infrastructure typically associated with developing and launching an app. Adopting PaaS can significantly reduce the management overhead of servers and networks.

A rolling strategy is the best to implement when needing to replace a cloud solution without interruptions and keeping costs low. This approach updates or replaces parts of the system gradually with minimal downtime and allows for a phased implementation.

These three measures help to secure the web server by implementing encryption and securing the authentication process. By disabling password authentication and enabling SSH key access only, the server is less vulnerable to brute-force attacks. Installing TLS certificates on the server helps to encrypt communications, preventing data interception and tampering.