For a load-balancing vServer with three identical backend servers using round-robin, what is the most efficient method to take one backend server offline for changes without affecting traffic to others?

• A. Disable the backend server entity targeted for change.
• B. Disable the load-balancing virtual server.
• C. Disable the backend service entity targeted for change.
• D. Unbind the correct server entity from the load-balancing virtual server.

Answer: (D)

Unbinding the specific server from the load-balancing vServer isolates that member from traffic while leaving the others intact. In round-robin, the vServer distributes requests only to the servers that are bound to it. By removing one bound backend, the distribution naturally shifts to the remaining two servers, so no traffic is sent to the offline one while the rest continue handling requests. This change is quick, easily reversible, and doesn’t affect the operation of the other bound servers or the overall vServer.

Disabling the backend server or backend service would mark that member as unavailable, which achieves a similar end but introduces additional steps and potential side effects like health-check state changes or longer propagation. Disabling the entire load-balancing virtual server would halt all traffic, which is far more disruptive.