Write through data protection guarantees that every write is written to disk synchronously, so that even in the event of a power failure or system crash no data is ever lost. The speed improvement is dramatic. Lazy write mode is even faster, but requires a UPS to prevent data loss, in a power failure. Data may be lost in the event of a system crash. Lazy write mode should be used with data that can be re-created in the event of a system crash, or for temporary files.