A linux server Farm 4. The proxy hardware is configured so that single points of failure are reduced as far as practicable. This farm is connected to the network via two AceDirector load-balancing switches. The ACEDirectors apportion proxy requests across the farm and monitor the response of the farm boxes. If one of the farm boxes dies then the AceDirectors will not send any further requests to that box.
Users simply see a single highly-available proxy service.
Each Director is connected to seperate switches at the front end, and the farm machines are distributed over two switches as well. Worst case scenario in the case of machine failure is if one of the switches serving at the farm end dies, in which case half the farm is unaccessible. This will in high load periods result in a slowdown, however service will still be maintained. If a preceeding switch or ACE dies then the other ACE will take over operations. This will result in a minimal timeout as the operational transfer takes place.