This graphic is divided into four sections. The top section depicts a person sitting at a computer. An arrow pointing down is labeled "1 Request." An arrow pointing up is labeled "8 Response." The second section depicts a computer in a cloud. An arrow pointing down is labeled "2 Calls." An arrow pointing up is labeled "3 Fan or error," and has an X through it. An arrow pointing down is labeled "4 Replay" and "5 Calls." The next section depicts five server computers in a cloud. The cloud is labeled "Database." Arrow 2 is pointing toward the computer on the left, which has an X through it. The server that is second from the left is pointing up to "3 Fan or Error." The arrow labeled "4 Replay" is pointing down to the fourth computer. The bottom section is labeled storage. The computers in the preceding section point down to four cylinders that represent disk storage.