Abstract: A data storage disk device for a RAID disk array is disclosed, comprising a rotatably mounted disk having a data storage surface; a first head for reading data from and writing data to the data storage surface; with a second head for reading data from the data storage surface; and control means for executing a write operation to a sector, said write operation including reading the contents of the sector via the second head for subsequent processing and writing new data to the sector via the first head, the first and second heads being arranged with respect to the data storage surface so that the new data can be written to the sector on the same revolution of the disk as the reading operation. The addition of a second head to the disk storage device improves performance of the disk device for RAID applications.

Abstract: A backup method for a computer database system comprising maintaining a mirrored copy of the database at a remote location is characterized in that updates to the remote database data are delayed for a delay time greater than or equal to the upper limit on the data communication delay between the local location and the remote location and updates to a remote log for the database are executed after corresponding updates to a local log without said delay. In this way a consistent copy of the database may be recovered from the mirrored copy of the database and the remote log after destruction of the database system.

Abstract: A limited multi-fault system and method manages error recovery in a local area network system. The system includes a data structure which store related error events, diagnostic problems and causes. In addition, a method of managing error events in real time and identifying causes and recommending actions is provided. A knowledge base is used to determine the causes and recommended actions for the problem.

Abstract: An expert based system for managing error events in a local area network (LAN) includes an inference engine and a knowledge base storing data defining a plurality of causal relationships. Each of the causal relationships associates an error message with a cause, at least one implied relationship, and at least one trigger relationship. The inference engine accesses said knowledge base in response to a receiver error message to identify the error message and retrieve from the knowledge base its possible causes. The received error message is compared with other already received error messages to filter out repeated error messages. Already received error messages are examined to determine whether a triggering error message has arrived and, if so, the received error is discarded.