Abstract: The disclosed computer-implemented method for monitoring data synchronization progress in a multi-hop data recovery system may include (i) calculating a number of data blocks to be synchronized, (ii) setting each element of a synchronization data structure to dirty, (iii) determining a dirty bytes counter, (iv) transmitting a portion of the data blocks to be synchronized, (v) receiving an acknowledgement corresponding to the transmitted portion of the data blocks, (vi) setting a set of elements within the synchronization data structure corresponding to the transmitted portion of the data blocks to clean, (vii) determining a pending dirty bytes counter that indicates a current number of elements within the synchronization data structure that are set to dirty, and (viii) transmitting the dirty bytes counter and the pending dirty bytes counter. Various other methods, systems, and computer-readable media are also disclosed.

Abstract: A method for fast I/O path failure detection and cluster wide failover. The method includes accessing a distributed computer system having a cluster including a plurality of nodes, and experiencing an I/O path failure for a storage device. An I/O failure message is generated in response to the I/O path failure. A cluster wide I/O failure message broadcast to the plurality of nodes that designates a faulted controller. Upon receiving I/O failure responses from the plurality of nodes, an I/O queue message is broadcast to the nodes to cause the nodes to queue I/O through the faulted controller and switch to an alternate controller. Upon receiving I/O queue responses from the plurality of nodes, an I/O failover commit message is broadcast to the nodes to cause the nodes to commit to a failover and un-queue their I/O.

Abstract: Systems and procedures may be used to coordinate the fail-back of multiple hosts in environments where the hosts share one or more data-storage resources. In one implementation, a procedure for coordinating fail-backs includes monitoring a failed data path to detect a restoration of the data path, polling remaining nodes in response to the restoration, and allowing the first node to resume communications if access has been restored to the remaining nodes.

Abstract: A method for fast I/O path failure detection and cluster wide failover. The method includes accessing a distributed computer system having a cluster including a plurality of nodes, and experiencing an I/O path failure for a storage device. An I/O failure message is generated in response to the I/O path failure. A cluster wide I/O failure message broadcast to the plurality of nodes that designates a faulted controller. Upon receiving I/O failure responses from the plurality nodes, an I/O queue message is broadcast to the nodes to cause the nodes to queue I/O through the faulted controller and switch to an alternate controller. Upon receiving I/O queue responses from the plurality nodes, an I/O failover commit message is broadcast to the nodes to cause the nodes to commit to a failure and un-queue their I/O.

Abstract: Systems and procedures may be used to coordinate the fail-back of multiple hosts in environments where the hosts share one or more data-storage resources. In one implementation, a procedure for coordinating fail-backs includes monitoring a failed data path to detect a restoration of the data path, polling remaining nodes in response to the restoration, and allowing the first node to resume communications if access has been restored to the remaining nodes.

Abstract: Systems, methods, apparatus and software can implement a SAN monitoring scheme for determining changes in SAN topology, such as device failure and state changes. These changes are recorded in a SAN topology data structure. Information in the SAN topology data structure is used, for example, to identify a suspect path or set of paths, and to make decisions about communications pathways used by a multipath device driver.

Abstract: A method for controlling data traffic within a storage area network can be provided. The method can comprise analyzing data for a path in a storage area network to determine whether the path should be identified as a less preferred path, and controlling data traffic routing to avoid use of a path identified as a less preferred path. In some embodiments, the data can be obtained from a host bus adaptor in the path. In some embodiments, the controlling can comprise throttling traffic over a path identified as a less preferred path.