What does the term 'throughput' refer to in server performance?

Throughput refers specifically to the amount of data transmitted in a specific time period, making it a critical metric for evaluating the performance of a server. This measurement is essential when assessing how efficiently a server can handle requests, especially under varying loads. High throughput indicates that a server can deliver large volumes of data swiftly, which is vital for applications such as streaming, large file transfers, or high-traffic websites.

In contrast, the other options deal with different aspects of server performance or capabilities. The total number of users connected simultaneously addresses user capacity rather than the data handling capability. The speed of the server's processor relates to computational power but does not directly measure data transmission capabilities. The total storage capacity of a server speaks to how much data it can hold, which is unrelated to how quickly data can be transmitted or processed. Thus, throughput is distinctively about the volume of data over time, making the selected answer accurate.