Abstract: 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.

Abstract: 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.

Abstract: 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. Access to a file by a processor node is controlled by tokens transferred to the node from a token manager. To prevent another processor node from removing a token after the token has been received, but before it performs the operation on the file, each process can lock the token after it has been received. A node with a token can lock a byte range of a file, which byte range may include all or only some of byte range cornered by the token.

Abstract: A computer system having a shared disk file system running on 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. Methods are provided for use as a parallel file system in a shared disk environment by use of a scalable directory, service for the system with a stable cursor, a segmented allocation map. Dynamic prefetch and cached balance pools for multiple accesses improve the system. Extended file attributes are used for implementation of Access Control Lists in a parallel file system, improvements to caching and cache performance developments balance pools for multiple accesses. A metadata node manages file metadata for parallel read and write actions.

Abstract: 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.