A technique for sharing a resource among a cluster of devices in a computer network. The technique involves generating a vote count that includes votes from voting devices attempting to form a cluster until the vote count reaches a quorum. The technique further involves, when the quorum is reached, selecting a most advanced generation indicator from among the voting devices, advancing the selected generation indicator and storing the advanced selected generation indicator in memory as a cluster generation indicator. Upon the advanced selected generation indicator being stored in memory, the cluster is formed and includes the voting devices. The technique further involves sharing a resource among the voting devices after the cluster is formed.
This computer implemented software invention supervises networked system resources with the goal of maximizing service availability, providing on-demand and uninterrupted access to service, and minimizing the down time due to failures. It is a cluster-wide solution that co-ordinates the states and activities of resources, assigns availability roles, implements recovery from failures, and implements overall system policy. To do this, it maintains a system model of the system's physical and logical configuration and models the resources using managed objects that provides an extensive representation of the states, roles, and relationships of the systems resources.
A mechanism that allows an application program running on a processor, to send data to a device using a medium that temporarily stores data and changes the order of the data dispatch on the way to the device. An inventive Random-In-First-Out (RIFO) buffer or memory device that restores the original order is provided. Several alternative approaches for implementing the RIFO control mechanisms for write efficiency and correctness. Method for use in conjunction with a data processing system having a host processor executing write instructions and communicating results in the form of symbols generated by the write instructions to at least one hardware device coupled to the host processor for receiving the symbols from the host processor, where the method preserves a predetermined order in which the symbols are received by the hardware device. Method includes sending a symbol from the host processor to a storage with an identifier indicating a symbol ordering relative to other of the symbols, storing the symbol and the indicator in the storage, and altering the order of dispatch of the symbols from the storage to the hardware device based on the indicator so that the symbols are received by the hardware device in the predetermined order independent of the order in which the symbols were communicated by the host processor. The invention also provides numerous embodiments of system, apparatus, method, computer program, and computer program product associated with the inventive concept.
One embodiment of the present invention provides a system that facilitates establishing a quorum for a cluster of computers that are geographically distributed. The system operates by detecting a change in membership of the cluster. Upon detecting the change, the system forms a potential new cluster by attempting to communicate with all other computers within the cluster. The system accumulates votes for each computer successfully contacted. The system also attempts to gain control of a quorum server located at a site separate from all computers within the cluster. If successful at gaining control, the system accumulates the quorum server's votes as well. If the total of accumulated votes is a majority of the available votes, the system forms a new cluster from the potential new cluster.
Dynamic reconfiguration of a quorum group of processors and recovery procedure therefore are provided for a shared nothing distributed computing system. Dynamic reconfiguration proceeds notwithstanding unavailability of at least one processor of the quorum group of processors assuming that a quorum of the remaining processors exists. Recovery processing is implementing by the group of processors so that the at least one processor which was unavailable during the dynamic reconfiguration of the group is able to obtain current state information once becoming active. Each processor of the group of processors includes an incarnation number and a list of member processors which participated in a commit process resulting in its incarnation number. The recovery processing includes exchanging the processors' incarnation numbers and lists of processors for propagation of the current state of the quorum group of processors to the at least one processor now becoming available. Determination of a relaxed quorum number for a quorum based operation of a distributed computing system is also described.
Dynamic reconfiguration of a quorum group of processors and recovery procedure therefore are provided for a shared nothing distributed computing system. Dynamic reconfiguration proceeds notwithstanding unavailability of at least one processor of the quorum group of processors assuming that a quorum of the remaining processors exists. Recovery processing is implementing by the group of processors so that the at least one processor which was unavailable during the dynamic reconfiguration of the group is able to obtain current state information once becoming active. Each processor of the group of processors includes an incarnation number and a list of member processors which resulted from a commit process resulting in its incarnation number. The recovery processing includes exchanging the processors' incarnation numbers and lists of processors for propagation of the current state of the quorum group of processors to the at least one processor now becoming available.
