Abstract: Various systems and methods for managing node connectivity in distributed storage systems are disclosed. For example, one method involves detecting a communication fault between two nodes. A first node is configured to communicate input/output (I/O) requests to the second node as in-flight I/O requests. The second node is configured to communicate locally generated I/O requests and the received I/O requests to storage devices. Once the communication fault is detected, a fencing operation is performed. The fencing operation can include processing some of the received I/O requests by the second node, and rejecting any additional in-flight I/O requests received from the first node.

Abstract: Various systems and methods for performing Input/Output (I/O) quiesce and drain operations in multi-node distributed storage systems are disclosed. For example, one method involves receiving a message. The message indicates a request for a operation to be performed by a node, where the node can receive I/O requests from an application, as well as remote I/O requests from another node. The node can issue the I/O requests and the remote I/O requests to the one or more storage devices. In response to receipt of the message, the method performs a first portion of a operation on the node. The first portion of the operation includes the node not processing any additional locally generated I/O requests and processing additional remote I/O requests.

Abstract: A system and method for determining a status of a connection path. For example, the method can include receiving a control message at a first node of a number of nodes that are configured to form a cluster, identifying a second node of the nodes as a node from which the control message was received, identifying a storage device to which the second node is coupled; and determining a status of a connection path. The connection path is between the first node and the second node, and the second node and the storage device. The first node includes a first computer system, and the second node includes a second computer system.

Abstract: A method and system for load balancing. The method includes discovering each of a plurality of hosts in a cluster, wherein the plurality of hosts is configured for accessing a LUN of a storage system through a storage network fabric. Global input/output (I/O) load characteristics are collected for each of the plurality of hosts at the device and/or volume level. A selected host is determined for processing an I/O originating at the local host, wherein the host is selected based on a current set of the global I/O load characteristics.

Abstract: Various systems and methods for managing node connectivity in distributed storage systems are disclosed. For example, one method involves detecting a communication fault between two nodes. A first node is configured to communicate input/output (I/O) requests to the second node as in-flight I/O requests. The second node is configured to communicate locally generated I/O requests and the received I/O requests to storage devices. Once the communication fault is detected, a fencing operation is performed. The fencing operation can include processing some of the received I/O requests by the second node, and rejecting any additional in-flight I/O requests received from the first node.

Abstract: A preferred node is selected for a specific functional role in a cluster. Dynamic and static parameters concerning the nodes are measured, including connectivity to shared storage. A user preference value is gleaned for each node, quantifying the user's preference of each corresponding node for the functional role. A preference rating is calculated for each node, based on the measured parameters and the gleaned user preference value. The preference rating indicates the node's suitability for the specific functional role, relative to the other nodes. Connectivity to shared storage in the cluster can be weighted more heavily than other parameters. Examples of specific functional roles in the cluster include becoming the master node, becoming a failover target for a specific application, or remaining in operation with access to shared cluster storage, in response to an occurrence of split brain.

Abstract: A system and method for discovering multiple paths to a disk device are disclosed. For example, the method can include discovering a plurality of paths that exist from a first host computer to a storage device. The plurality of paths includes at least one local path and at least one network path from the first host computer to the storage device. In addition, the first host computer is one of several host computers in a cluster. Once the paths have been discovered, a representation of the paths from the first host computer to the storage device is generated. Such a method can be performed, for example, without user intervention.

Abstract: A reconfiguration is distributed among multiple nodes of a cluster. Upon detecting an initiation of a reconfiguration of the cluster, reconfiguration functionality is delegated from the master node to one or more slave nodes in the cluster. Thus, multiple nodes perform reconfiguration functionality in parallel, such that one or more slave nodes perform delegated reconfiguration tasks that would conventionally be performed by the master node. The cluster reconfiguration can be in the form of one or more nodes joining or leaving the cluster. Data to facilitate the cluster reconfiguration can be transmitted from the master node to a slave node to which reconfiguration functionality is being delegated. Such data can include, for example, identifiers of nodes joining or leaving the cluster and/or information concerning the architecture and shared storage media of the cluster.

Abstract: A method and system for load balancing. The method includes discovering each of a plurality of hosts in a cluster, wherein the plurality of hosts is configured for accessing a LUN of a storage system through a storage network fabric. Global input/output (I/O) load characteristics are collected for each of the plurality of hosts at the device and/or volume level. A selected host is determined for processing an I/O originating at the local host, wherein the host is selected based on a current set of the global I/O load characteristics.