Release It!

Defining Capacity

Marketers and managers toss words such as performance and capacity around with casual abandon. Architecture and development requires more precision. At the risk of being pedantic, let me define some terms.

Performance measures how fast the system processes a single transaction. This can be measured in isolation or under load. The system’s performance has a major impact on its throughput. Even if using the word performance, the customer does not really care about performance. Customers are interested in either throughput or capacity. End users, on the other hand, don’t care about overall capacity; they care only about the performance of their own transactions. They can’t log in to the servers to see whether the applications ...