Abstract: Systems, methods, apparatus and software can configure, support, and make use of a coordinator virtual device to determine which node or nodes of a cluster should be ejected from the cluster as a result of a cluster partition or other error event. Fencing software operating on the cluster nodes monitors the cluster for a cluster partition (split-brain) event, and when such an event occurs, software on the nodes attempts to gain control of the coordinator virtual device. A node that succeeds in gaining control of the coordinator virtual device survives. Nodes failing to gain control of the coordinator virtual device remove themselves or are removed from the cluster. The coordinator virtual device can be established by a virtual device configuration server which provides coordinator virtual device access to cluster nodes acting as virtual device configuration clients.

Abstract: A system or method for creating a point-in-time (PIT) or backup copy of one or more data volumes using a roll-back log. The backup copy can be created without employing hot backup mode. In one embodiment, the method includes copying data blocks of a volume to a backup memory configured to store a backup copy of the volume, wherein the data blocks are sequentially copied until all of the data blocks of the volume are copied to the backup memory. A first request is generated to overwrite existing data of a first data block of the volume with new data before all of the data blocks of the volume are copied to the backup memory. Before overwriting the existing data and before all of the data blocks of the volume are copied to the backup memory, the existing data is copied to a first memory (e.g., the roll-back log). Before all of the data blocks of the volume are copied to the backup memory, the existing data is overwritten with the new data.

Abstract: A system and to prevent data corruption due to split brain in shared data clusters includes two or more nodes of a cluster, a shared storage device, and an update manager. The update manager may be configured to maintain a local persistent store corresponding to each node of the cluster. On receiving an update request directed to the shared storage device from a first node, the update manager may be configured to redirect the update to the local persistent store corresponding to the first node. The update manager may be further configured to verify a cluster membership status of the first node, and to transfer the contents of the update from the local persistent store to the shared storage device if the cluster membership verification succeeds.

Abstract: A method, system, application programming interface, computer system and computer program product to provide locks for controlling access to data by nodes in a multi-node system while minimizing the number of messages sent between nodes. Locks can be grouped into blocks of locks, and exclusive access to data protected by locks in a block of locks can be granted together to a block agent for a particular node. The block agent handles requests for access to the data on behalf of clients running on the respective node. The block agent sends a message to a block master running on another node only when a request is made for access to data to which the block agent has not already obtained access. Access can be granted to a block agent for an entire block or for a portion of a block of locks.

Abstract: A system and method for adaptively responding to update messages for a replica of a data object. A node may maintain first information regarding a replica of a data object. In various embodiments, the first information may comprise any kind of information regarding the replica of the data object. In one embodiment, the first information may comprise information indicative of accesses to the replica of the data object, e.g., may comprise access history information. In response to receiving a message for updating the replica of the data object, the node may respond to the message based on the first information. For example, the node may select one or more operations to perform based on the first information and may perform the one or more selected operations.

Abstract: A plurality of virtual circuits, each including at least two network nodes, may be established over a single network connection for inter-process messaging. The network connection may be opened asynchronously via a non-blocking open. A virtual circuit including three or more nodes may be implemented in a star formation or a relay formation. Messages may be sent as unicast or broadcast messages. An additional virtual circuit may be opened for the purpose of transmitting status information regarding the network connection between the networked computer systems.

Abstract: Systems, methods, apparatus and software can make use of separated I/O processors and strategy processors (implemented in hardware and/or software) to perform virtual device I/O operations. I/O processors operating on cluster nodes, storage appliance ports, or other devices can receive I/O operation requests directed to virtual devices, e.g., volumes or virtual logical units. Information about the request is forwarded to a strategy processor, operating independently or as part of larger volume management software where corresponding physical device I/O operations are determined. The physical device I/O operations can include additional information about the operations, e.g., tag information and summary information, for use in processing the virtual device I/O request. The physical device I/O operations are sent back to the I/O processor which executes the operations and/or passes the operation on to the appropriate storage device.

Abstract: The disclosed technology can be used to develop systems and perform methods that receive and process I/O requests directed to at least a part of a logical unit of storage. The I/O requests can be associated with different times corresponding to when such I/O requests were received. Nodes that include non-overlapping address ranges associated with the logical unit of storage can be formed in response to receiving the I/O requests and such nodes can be subsequently organized into a tree data structure. The tree data structure can serve as a basis for determining address overlap, for example to enable processing a first operation associated with a first one of the I/O requests in accordance with the first I/O request's receipt time, while one or more other operations associated with a different I/O request may be processed irrespective of that different I/O request's receipt time.

Abstract: Procedures and systems for avoiding undesired trespass may be deployed in host processors that use storage arrays with automated fail-back and fail-over functions. In one embodiment, a method may synchronize path records in a storage array with path records in a host processor. The method may detect a failure of a first data path through a first controller on the storage array to a logical unit (LUN) on the storage array. In response to the failure, the host processor may initiate a failover on the storage array of the LUN, so that the LUN is accessed through a backup controller on the storage array. The host processor may also issue commands to pin the failed-over LUN to the backup controller. For example, the host processor may issue commands to set the default owner of the LUN to be the backup controller.

Abstract: A system and method for creating and utilizing dynamic directories in a computing system. A computing system includes a file system and a dynamic directory mechanism. The dynamic directory mechanism is configured to enable a user to create dynamic directories which are identifiable as having special behaviors associated with them. The user may create executable instructions for performing the special behaviors in a user space of an operating system and associate the special behaviors with selected native file system operations which may be performed on the directory. In response to detecting an operation on a directory is initiated, the mechanism determines whether the directory is a dynamic directory. If the directory is a dynamic directory, the mechanism determines whether any predetermined special behaviors have been defined for the initiated operation and if so performs the special behaviors.

Abstract: A system and method for managing the environment of software processes in a computer system. A computer system comprises a processor and at least one process environment comprising one or more environment variables. The processor executes one or more processes, intercepts the launch of a process, sets at least one environment variable to a first value, and continues the launch of the process. Setting the environment variable may enable a profiler process. The processor may set at least one environment variable for the process to a value which is chosen irrespective of a value of the environment variable of a parent process of the process. Further, the processor may set at least one environment variable for the process to a default value if a data repository does not contain an entry that has an identification which corresponds to the process.

Abstract: A method for identifying a time at which first data was written to a data store. A data store is configured to respond to data requests made to the data store with the data in the data store at a first time in the past. The method can be used to identify a time, for example, at which a data store was corrupted.

Abstract: In a data storage system, a storage management device includes at least a target mode driver, a data classifier in communication with the target mode driver, a plurality of storage buffers in communication with the target mode driver, a plurality of I/O managers in communication with the data classifier, and a physical store interface in communication with the plurality of I/O managers and with the plurality of storage buffers.

Abstract: Various embodiments of systems and methods are disclosed for using priority information when handling error conditions for a storage resource. In some embodiments, a method involves detecting an error condition, which is associated with a storage resource, and selecting an error-correcting action in response to detection of the error condition. Selection of the error-correcting action is based on priority information. The priority information identifies respective priorities of several applications. At least one of the applications uses the storage resource when accessing application data.

Abstract: A method, system and computer accessible medium for expiring access tokens in preparation for freezing file images. A metadata server may maintain a next scheduled quiesce time and may issue access tokens configured to expire before the next scheduled quiesce time. A metadata server may set an access token's expiration time to a maximum expiration time indicated by the next scheduled quiesce time or may set an access token's expiration time to a default expiration time if the default expiration time is earlier than the maximum expiration time. A storage device may recognize and enforce the access token's expiration time.

Abstract: Systems and methods for I/O fencing in a shared storage environment are provided. Prior to initiating an I/O request, when feasible, the current time from a local timer is compared to the current state of an interval obtained for the target device. As a result, a device reset occurring while the interval is viable does not arbitrarily end a multiphase I/O operation. However, a device reset occurring once the lease has expired results in a delay or termination of the multiphase I/O operation. As a result, multiphase I/O operations from initiating hosts that have lost contact with the shared storage environment are not allowed to corrupt the shared storage devices.

Abstract: A method, system, computer system, and computer-readable medium to perform root cause analysis of failure of an application program in a clustering environment. Upon the occurrence of a problem or event of interest, cluster configuration data can be obtained to provide a common context for events occurring at different software layers supporting an application. Diagnostic information produced by the different software layers can be obtained from various log files, which are typically in different formats and on different nodes in the cluster. The diagnostic information can be viewed in the context of the cluster and filtered to identify events related to the failure. The related events can be presented in a time-ordered sequence to assist in analysis of the event of interest. Patterns of events that led to the failure can be identified and documented for use in further problem analysis and for taking preventative and/or corrective measures.

Abstract: A cluster comprises a plurality of computer systems, wherein each of the plurality of computer systems is configured to execute one or more virtual machines. Each of the plurality of computer systems comprises hardware and a plurality of instructions. The plurality of instructions, when executed on the hardware, migrates at least a first virtual machine executing on a first computer system of the plurality of computer systems to a second computer system of the plurality of computer systems. The plurality of instructions migrates the first virtual machine responsive to a first load of the first computer system prior to the migration exceeding a second load of the second computer system prior to the migration.

Abstract: Methods, systems, and apparatus can provide individual users of a computer system a means to share their quotas to resources accessible through that system. In one embodiment, this is accomplished, in part, by providing a shared quota descriptor understood by a file system and that can be manipulated by individual users. To that end, the present invention further provides individual users access to mechanisms by which to create and adjust shared quotas.

Abstract: An apparatus or method for preserving the relationships or dependencies between content of files in a file system or between content of files in separate file systems. The preservation of relationships or dependencies may require the preservation of the files and their content as well. In one embodiment, the method includes receiving a first instruction that, when implemented, performs an operation involving a first file in a file system, wherein the first file is related to the second file. In response to receiving the first instruction, a second instruction is selected that, when implemented, performs a second operation involving the first file or a second file, wherein the second instruction is implemented before or after implementing the first instruction.