Clustered Web Server Model 1 2 File Server 3 Cache Dispatcher (Front End) Manager N Object Store Web Clients Server Nodes

Server Parameters Num server nodes Mem cache size Disk cache size Cache replacement policy for each (LRU, LFU, SIZE, DUAL) Comm. latency Cache consistency Dispatch policy (DNS, RR, Redirect, Load) Request distribution policy (requests, bw, conns, affinity, ...) Server bandwidth Per-request bandwidth BW scaling model

Performance Metrics Load balancing requests bytes bandwidth connections clients Relative improvement versus RR, Rand, etc Cache performance document hit rate byte hit rate Comm. overhead Avg response time Avg inflation factor Others...