Multiple applications request data from multiple storage units over a computer network. The data is divided into segments and each segment is distributed randomly on one of several storage units, independent of the storage units on which other segments of the media data are stored. At least one additional copy of each segment also is distributed randomly over the storage units, such that each segment is stored on at least two storage units. This random distribution of multiple copies of segments of data improves both scalability and reliability. When an application requests a selected segment of data, the request is processed by the storage unit with the shortest queue of requests. Random fluctuations in the load applied by multiple applications on multiple storage units are balanced nearly equally over all of the storage units. This combination of techniques results in a system which can transfer multiple, independent high-bandwidth streams of data in a scalable manner in both directions between multiple applications and multiple storage units.

Computer system and process for transferring multiple high bandwidth streams of data between multiple storage units and multiple applications in a scalable and reliable manner

Multiple applications request data from multiple storage units over a computer network. The data is divided into segments and each segment is distributed randomly on one of several storage units, independent of the storage units on which other segments of the media data are stored. Redundancy information corresponding to each segment also is distributed randomly over the storage units. The redundancy information for a segment may be a copy of the segment, such that each segment is stored on at least two storage units. The redundancy information also may be based on two or more segments. This random distribution of segments of data and corresponding redundancy information improves both scalability and reliability. When a storage unit fails, its load is distributed evenly over to remaining storage units and its lost data may be recovered because of the redundancy information. When an application requests a selected segment of data, the request may be processed by the storage unit with the shortest queue of requests. Random fluctuations in the load applied by multiple applications on multiple storage units are balanced nearly equally over all of the storage units. Small data files also may be stored on storage units that combine small files into larger segments of data using a log structured file system. This combination of techniques results in a system which can transfer both multiple, independent high-bandwidth streams of data and small data files in a scalable manner in both directions between multiple applications and multiple storage units.

Computer system and process for transferring streams of data between multiple storage units and multiple applications in a scalable and reliable manner

A distributed data storage system for sharing data among client computers running different types of operating systems by separating metadata from data. Data is stored in storage pools that are accessed by the client computers through a storage network. Metadata is stored in a metadata store and provided to the client computers by a cluster of metadata servers. The client computers communicate with the metadata servers using a Storage Tank protocol and over a control network. Each client computer runs an operating system-specific client program that provides the client side functions of the Storage Tank protocol. The client program preferably includes a file system interface for communicating with the file system in the storage system and user applications, a client state manager for providing data consistency, and a plurality of operating system services for communicating with the metadata servers.

A distributed storage system for data-sharing among client computers running different operating system types

The invention provides a method, system, and computer program product to control the access, copying, and/or transfer of a digital asset by mobile, wireless devices using a digital voucher. The digital voucher references a primary content that contains all of the expression for that particular asset and a secondary content that contains information that can be distilled out as a preview. The information in the primary content can be limited to a specified duration or a specific number of viewings. The author, owner, or possessor of the digital asset specifies the terms and conditions for distribution of the digital asset. The digital voucher authorizes the mobile, wireless device to access a specified primary or secondary content that may be located elsewhere in the network. The mobile, wireless device can download a copy of portions or all of the content depending on the terms specified in the voucher.

Digital rights management in a mobile communications environment

An on-line services network includes application servers and Gateway microcomputers that are interconnected by a LAN. The Gateway microcomputers receive service requests which are transmitted over a WAN from client microcomputers operated by end users. Upon receiving a request to open a service, the Gateway microcomputers access a periodically-updated service map to locate the replicated application servers that are currently running the corresponding service application, and then apply a load balancing method (using server load data contained within the service map) to select an application server that has a relatively low processing load. A communications protocol between the client and Gateway microcomputers enables users to access multiple services simultaneously. A hot redirection technique allows a user service session to be transferred from one application server to another (replicated) application server without termination of the service session. Various mechanisms are provided for efficiently reallocating application servers to different on-line services, and for allowing additional servers to be efficiently added to the network.

Method of redirecting a client service session to a second application server without interrupting the session by forwarding service-specific information to the second server

A computer system having a shared disk file system running on multiple computers each having their own instance of an operating system and being coupled for parallel data sharing access to files residing on network attached shared disks. A metadata node manages file metadata for parallel read and write actions. Metadata tokens are used for controlled access to the metadata and initial selection and changing of the metadata node.

Parallel file system with method using tokens for locking modes

A system and method for non-disruptive recovery from a file server failure. State information for a file system managed by a server is maintained among a plurality of client nodes of a distributed system. When a failure of the server is detected, all ongoing requests to server are suspended. Then, the state information in each client node is transferred to an identified back-up server. Based on the state information, the file server state prior to the failure is reconstructed. After the reconstructing the file system, the suspended requests are restarted on the back-up server.

Non-disruptive recovery from file server failure in a highly available file system for clustered computing environments

A system and method for avoiding serialization on updating the modification time of files in a cluster system. In accordance with the method, the modification time field of a file can be accessed by multiple readers or multiple writers and each client in the cluster system can update their own copy of the modification time. Whenever a client requests to read the modification time, the copies of the modification time are reconciled. The copies of the modification times are also reconciled when a cache flush or synchronization operation forces such reconciliation. The present system and method supports the requirement (of certain operating systems such as UNIX) that an explicit user-issued command to set the modification time is accomplished by granting an exclusive-write mode for the modification field.

Simultaneous updates to the modification time attribute of a shared file in a cluster having a server and client nodes

A computer system having a shared disk file system running on multiple computers each having their own instance of an operating system and being coupled for parallel data sharing access to files residing on network attached shared disks. Locking techniques reduce the overhead of a token manager which is also used in the file system recovery if a computer participating in the management of shared disks becomes unavailable or failed. Synchronous and asynchronous takeover of a metadata node occurs for correction of metadata which was under modification and a new computer node to be a metadata node for that file. Locks are not constantly required to allocate new blocks on behalf of a user.

Parallel file system and method for independent metadata loggin

In a fault-tolerant distributed file system, the server state needs to be reconstructed after the server restarts or when its function is taken over by another node. A crucial part of the server state is determining whether or not in-flight, directory-operations initiated by the clients have been completed. Described is a check-before-request scheme that solves this problem. A global lock is obtained on the directory or directories first. A check is made on the directories to see if the operation would succeed, and if so a request is made to the server for the operation. If the server were to fail during the execution of the operation, completion of the operation prior to failure can be determined by merely re-examining the directory contents.

William A. Kish

Papers

Parallel file system with method using tokens for locking modes

Non-disruptive recovery from file server failure in a highly available file system for clustered computing environments

Simultaneous updates to the modification time attribute of a shared file in a cluster having a server and client nodes

Parallel file system and method for independent metadata loggin

Scheme to determine completion of directory operations for server recovery