International Business Machines Corporation

Robert Douglas Tennison

Warren B Harding

Charles Edwin Hoff

James Clair Young, Jr

William O Vomaska

Patrick Fred DeJohn

A peripheral data storage hierarchy includes three storage levels. The top storage level is a fast accessing direct access storage device(s), such as magnetic disk drives. The intermediate level is an automatic warehouse type library, storing a large plurality of optical disks, which are automatically transferred between storage cells of the library and optical disk drives operatively connected to the host processor. The bottom level of the storage hierarchy includes one or more stand-alone optical disk drives and a shelf unit. Personnel manually carry the optical disks between the stand-alone drives and the shelf unit upon mount and demount commands received from the host processor. The intermediate library level uses the same type of optical disk as used in the bottom level of the data storage hierarchy. An I/O station in each of the automatic libraries enables manual access to the optical disk for transferring the optical disks between the intermediate and bottom levels. Preferably, the transfer is only from the intermediate level to the bottom level. Access to named storage objects in disks stored in the bottom level are through the stand-alone drives. A host processor has an independent access path to each level of the data storage hierarchy. A directory and other data structures indicate the number of copies made of each named data object and the location of such copies, such that the host processor 10 can independently access a copy from any level of the data storage hierarchy.

Multi-level peripheral data storage hierarchy with independent access to

A virtually addressed multilevel mass storage system (MSS) has error recovery and definition procedures and apparatus for controlling and enabling recovery from error conditions in an upper storage level. A plurality of possible error conditions in an upper level gives rise to errors in destaging data signals to a lower level, plus possible overwriting good data with data in error. A first such error condition is a data error detected during a destage. A second such error condition is repeated upper-level equipment (not data) errors. Both errors make data integrity of the lower-level suspect. Corrective action for a plurality of errors includes coordination with a host computer, reconfiguration, destaging data in error after precautionary steps, and preserving data in error at the failing upper level unit which is used in virtual mode except for the portion yielding the error condition.

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Boulder, CO, United States of America

Robert Douglas Tennison