Lucent Technologies Inc.

Bruce K Hillyer

Elizabeth A Shriver

Yossi Matias

Abraham Silberschatz

Jeffrey S Vitter

Rakesh D Barve

Bjorn Markus Jakobsson

Rajeev R Rastogi

Banu Rahime Ozden

Eran Gabber

Phillip B Gibbons

Alexandros Biliris

Euthimios Panagos

Wee Teck Ng

Phillio B Gibbons

A data replication system is disclosed in which replication functionalities between a host computer, an interconnecting computer network, and a plurality of storage devices are separated into host elements and a plurality of storage elements. The host computer is connected to one or more host elements. The host element is responsible for replicating data between the storage devices, which are each connected to an associated storage element, and for maintaining data consistency. Further, the host element instructs a storage element whose associated storage device does not contain up-to-date data to recover from another one of the plurality of storage elements and its associated storage device. The storage elements and their associated storage devices may be located in any combination of diverse or same geographical sites in a manner to ensure sufficient replication in the event of a site or equipment failure. The storage elements are responsible for executing read and write requests received from the host computer and for maintaining data consistency. When a storage element and its associated storage device is determined not to contain up-to-date data, recovery is effected by data transfer from one of the other storage elements and its associated storage device, that is indicated by the host element. Such recovery is done directly between the respective storage elements and associated storage devices, without transiting the data through the host element.

Redundant data storage and data recovery system

The present invention is an apparatus for generating random bits from a computer system. The apparatus comprises a rotating storage device operating within the computer system. A rotational latency of the rotating storage device is associated with the computer system accessing information from the storage device with the rotational latency causing the accessing of the information to have an entropy. An extraction mechanism extracts random bits derived from entropy of the rotational latency of the storage device.

Storage device random bit generator

A method for scheduling access of data blocks located in a computer system having a plurality of disk drives, each disk drive has a disk cache with a specified fence parameter value coupled to a host computer via a common bus. The method according to one embodiment, comprises the steps of: (a) sequentially accessing each of the disk drives for a predetermined number of iterations to retrieve a predetermined number of data blocks; (b) for a specified number of the iterations, transferring data located in the disk cache to be transferred to the common bus and requesting data corresponding to the following iteration to be transferred to the disk cache; and (c) repeating steps (a) and (b) until the predetermined iterations are completed.

System and method for modeling and optimizing I/O throughput of multiple disks on a bus

A dynamic process for improving the performance of a tape-based storage system is disclosed which takes a global view with regard to scheduling and tape selection. All requested data blocks located on multiple tapes within the storage system are analyzed and, taking advantage of the existing replication of some of the requested data blocks on multiple tapes and the location of the data blocks on the tapes, a schedule is formed that results in the reading/downloading of requested data blocks in an efficient manner.

Efficient scheduling of reading data from multiple storage mediums to satisfy multiple requests

A method for estimating and read durations, in response to requests to read data blocks stored in the disk drives in a computer system having a plurality of disk drives. Each disk drive has a disk cache with a non-zero fence parameter value coupled to a host computer via a common bus. The method according to one embodiment, comprises the steps of: (a) measuring an overhead period corresponding to the time during which a request to read is transmitted to a disk drive via the bus; (b) measuring an expected minimum positioning time corresponding to the shortest time required for a disk drive to locate said data block; (c) measuring mechanism-to-cache read time corresponding to the time required for a disk drive to transfer a data portion B,to a disk cache; (d) measuring the time required to transfer data blocks stored in each of said disk caches to the host; and (e) adding the times measured at steps (a) through (d).

An apparatus and method is provided that supports continuous media for conventional networked workstations and PC's. Described are user-level mechanisms and policies designed to give good, efficient multimedia service under the mild assumption that the operating system provides a preemptive real-time scheduling class that can be used to give CPU cycles to the multimedia processes in preference to other processes that are not time sensitive. There are no modifications to the operating system kernel and isochronous networks are not required. It suffices for an application to state that it wants to play a particular stream of a type known to the server (e.g. a file containing MPEG-1 video 320.times.240 pixels, 8-bit color, 30 frames per second), or for the application to specify a frame rate and an index describing the offset of each frame in a file.

Dynamic hierarchical network resource scheduling for continuous media

A system for scheduling read-requests for a serpentine data tape. The transit time between arbitrarily selected locations in the tape is not a linear function of distance between the locations. Despite this non-linearity, a model has been developed which accurately predicts such transit times. Using the model, a list of read-requests is re-organized into a sequence requiring a minimal, or at least smaller, total time to execute.

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Lebanon, NJ, United States of America

Bruce K Hillyer