Instead of requiring one server to wait on another, server clustering allows each server to act on its own while using one common, redundant mass storage device. In a basic server cluster, two servers would share one RAID array. If one server goes down, the second takes over while still maintaining its own workload. The failover time is greatly reduced becauseeach server is already attached to the information that usersare seeking.
Also, there is less chance that data will be lost during a system failure. Data does not have to be sent to a backup system at time of failure, because it is already in both servers. Just as important, the cost factor is reduced since it is not necessary to have a separate RAID array in each server, and the backup server is not merely waiting for something to do. It is functioning as an active production server on the network, sharing the processing load.