Digi-data Corporation

Raymond Duchesne

Tomlinson G Rauscher

Kenneth Lewis Willis

A 'Logging' method and apparatus is provided to protect control unit cached data not yet written to backing storage disk drives. This recording mechanism copies 'WRITE DATA' to a log at a target logically external or physically external to storage control units which are connected to a common storage pool and constitute a set. Upon failure of one of the set of control units, the &#x201c;Log&#x201d; information is available to insure that pending &#x201c;write&#x201d; data is written to the proper location on the disk drives of the storage pool upon a recovery action. One of surviving members of the set assumes control of the storage managed by the failing control unit by utilizing the recorded information to insure that data not written to backing storage (disks) up to the point of failure is then written to the disk backing storage. The surviving member of the set recovering the failing control unit storage (disk set) ownership effects a &#x201c;flush&#x201d; of (WRITE) the Journaled WRITE DATA to the backing storage disk drives before allowing normal operations to proceed.

Storage control unit with memory cache protection via recorded log

A device and method for connection to a host and transferring data between the host and data storage assembly. The device is preferably a storage system which initializes a logical unit (LUN) in the storage assembly. A persistent memory stores a data representation of clean areas in the LUN. The storage system receives data to be written from the host to a destination area in the LUN, and determines if the destination area in the LUN is a clean area or a dirty area as indicated in the persistent memory. The storage system effects a snapshot copy of data from the destination area in the LUN to an archive storage device of the storage assembly only if the destination area is not entirely a clean area. Bandwidth is likewise reduced in LUN copy and reconstruction operations.

Method to accelerate block level snapshots in archiving storage systems

The RAID system of this invention is able to function with undiminished capacity despite the failure of any one DASD, connector, or storage array controller. A signal is produced when any component fails, thereby alerting the operator of the need to replace the failed component. The reliability of this RAID system is achieved by using two connectors for each connection, by using a spare DASD for each channel of DASD, and by providing a passive storage array controller able to assume the identify of and take over the control of the DASD controlled by a failed storage array controller. This is a reliable, inexpensive system for achieving unprecedented reliability in the storage and delivery of data.

Growing community of inventors

Round Hill, VA, United States of America

Raymond Duchesne