disaster recovery systems, this mirroring may not be done by integrated systems but simply by additional applications on primary and secondary machines. Additional benefits In addition to providing an additional copy of the data for the purpose of redundancy in case of hardware failure, disk mirroring can allow each disk to be accessed separately for reading purposes. Under certain circumstances, this can significantly improve performance as the system can choose for each read which disk can seek most quickly to the required data. This is especially significant where there are several tasks competing for data on the same disk, and thrashing (where the switching between tasks takes up more time than the task itself) can be reduced. This is an important consideration in hardware configurations that frequently access the data on the disk. See also Disk cloning Distributed Replicated Block Device (DRBD) Mirror site Stable storage References Fault-tolerant computer systems RAID