Highly available cluster message passing facility

Abstract

A cluster implements a virtual disk system that provides each node of the cluster access to each storage device of the cluster. The virtual disk system provides high availability such that a storage device may be accessed and data access requests are reliably completed even in the presence of a failure. To ensure consistent mapping and file permission data among the nodes, data are stored in a highly available cluster database. Because the cluster database provides consistent data to the nodes even in the presence of a failure, each node will have consistent mapping and file permission data. A cluster transport interface is provided that establishes links between the nodes and manages the links. Messages received by the cluster transports interface are conveyed to the destination node via one or more links. The configuration of a cluster may be modified during operation. Prior to modifying the configuration, a reconfiguration procedure suspends data access requests and waits for pending data access requests to complete. The reconfiguration is performed and the mapping is modified to reflect the new configuration. The node then updates the internal representation of the mapping and resumes issuing data access requests.

Description

[0001] 1. Field of the Invention[0002] This invention relates to the field of distributed computing systems and, more particularly, to distributed virtual storage devices.[0003] 2. Description of the Related Art[0004] Distributed computing systems, such as clusters, may include two or more nodes, which may be employed to perform a computing task. Generally speaking, a node is a group of circuitry designed to perform one or more computing tasks. A node may include one or more processors, a memory and interface circuitry. Generally speaking, a cluster is a group of two or more nodes that have the capability of exchanging data between nodes. A particular computing task may be performed upon one node, while other nodes perform unrelated computing tasks. Alternatively, components of a particular computing task may be distributed among the nodes to decrease the time required perform the computing task as a whole. Generally speaking, a processor is a device configured to perform an operati...

AI Technical Summary

Benefits of technology

[0014] One feature of a virtual disk system in accordance with the present invention is the high availability of the system. In one embodiment, the virtual disk system stores all of the data access requests it receives and retries those requests if an error occurs. For example, the virtual disk system of a node that initiates a data access request, called a requesting node, may store all outstanding data requests. If the destination node, i.e. the node to which the data access request is directed, is unable to complete the data access request, an error indication may be returned to the requesting node and the requesting node may resend the data access request to an alternate node that is connected to the storage device. This error detection and retry is performed automatically and is transparent to the client. In another example, if a node failure occurs, the virtual disk system may receive a modified list of active nodes and resend incomplete data access requests to active nodes coupled to the storage device. This reconfiguration and retry also is transparent to the client.

[0015] Another feature of a virtual disk system in accordance with the present invention is the ability to reconfigure the cluster while the cluster is operating. When a cluster is reconfigured, the mapping of virtual disks to storage devices may be updated. To prevent errors, a synchronization command may be performed or operated to all the nodes of the cluster prior to updating the mapping. The synchronization command causes the nodes to stop issuing data access requests. After the mapping is updated, another synchronization command causes the node to resume issuing data access requests.

Problems solved by technology

Unfortunately, conventional virtual disk systems do not guarantee a consistent virtual disk mapping.

Conventional virtual disk systems cannot support a volume manager layered either above or below the storage devices.

Unfortunately, conventional systems do not provide a reliable means of ensuring that the representations on each node have consistent permission data.

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