What is a key feature of blade servers?

A key feature of blade servers is their energy efficiency and compact design. Blade servers are specifically engineered to save space and improve power consumption in data centers. They have a modular architecture that allows multiple server blades to fit into a single chassis, sharing power, cooling, and management resources, which significantly reduces the overall footprint. This compact design enables organizations to maximize their server capabilities while minimizing the physical space needed for deployment, thus leading to enhanced energy efficiency.

The other options highlight characteristics that do not accurately represent blade servers. For instance, large physical structures and fixed hardware configurations are contrary to the flexible and space-saving nature of blade technology. Additionally, high costs with minimal performance do not align with the value proposition of blade servers, which are favored for their efficiency and performance capabilities in managing workloads.