287 results about "Exclusive access" patented technology

Access by multiple hosts, such as computers, to a data storage device by way of a network while maintaining data integrity. In one embodiment, a method for accessing the storage device includes acquiring a resource “lock” that provides exclusive access to one of the hosts at a time. In another embodiment, the file systems of a first and second host provide file system attributes stored in a storage device to provide mutually exclusive access for each host to free blocks of the device. In another embodiment, a networked system contains a first host having exclusive direct access to a storage device over a digital network. A second host requiring access to the storage device communicates with the first host by way of the digital network. File access requests generated by the second host are transferred by a redirection filter driver within the second host to the first host.

The invention provides both interfaces of SAN and NAS, prevents data miss even when a trouble occurs and makes it possible that an arbitrary number of NAS interfaces access the same file system with high performance. A storage system includes multiple interfaces for external connection, multiple disks accessed from multiple interfaces, and a shared memory accessed from multiple interfaces. The multiple interfaces are block interfaces executing disk block I / O request, and file interfaces of file servers executing file I / O request. A file system in the file servers is constructed in a part of the disks, and a log storage area holding change log of the file system, and a management file server information storage area holding information of managing file server performing exclusive access control of file system and management of log storage area are formed in the shared memory.

A mechanism for recording a timing in which a high urgency process is started is provided, and upon entry to a critical section in the middle of a low urgency process, by referencing the record, it is inspected whether a high urgency process will be started during execution of the critical section. If it will not be started, the critical section is entered, and if it will be started, control is exerted so that entry to the critical section is postponed until the high urgency process is completed. Exclusive access control in a critical section can be performed suitably under conditions where a plurality of task execution environments exist.

Multiple competing processors cooperatively manage access to a shared resource. Each processor separately stores a lock table, listing shared resource subparts, such as memory addresses of a data storage device, for example. The lock tables are stored in nonvolatile storage. In each lock table, each subpart is associated with a "state," such as; LOCAL or REMOTE. In response to access requests from the hosts, the processors exchange various messages to cooperatively elect a single processor to have exclusive access to the subparts involved in the access requests. After one processor is elected, the lock-holding processor configures its lock table to show the identified subpart in the LOCAL state, and all non-lock-holding processors configure their lock tables to show the identified subpart in the REMOTE state. Thus, rather than replicating one lock table for all processors, the processors separately maintain lock tables that are coordinated with each other. Importantly, each processor honors its lock table by refraining from accessing a subpart of the shared resource unless the processor's lock table indicates a LOCAL state for that subpart. In one embodiment, optimized for the two processor environment, the messages exchanged by the processors include lock request, lock release, and lock grant messages.

An architecture for a read / write thread lock is provided for use in a computing environment where several sets of computer instructions, or “threads,” can execute concurrently. The disclosed thread lock allows concurrently-executing threads to share access to a resource, such as a data object. The thread lock allows a plurality of threads to read from a resource at the same time, while providing a thread exclusive access to the resource when that thread is writing to the resource. The thread lock uses critical sections to suspend execution of other threads when one thread needs exclusive access to the resource. Additionally, a technique is provided whereby the invention can be deployed as constructors and destructors in a programming language, such as C++, where constructors and destructors are available. When the invention is deployed in such a manner, it is possible for a programmer to issue an instruction to lock a resource, without having to issue a corresponding unlock instruction.