Methods, systems and computer program products for maintaining components of networked nodes with distributed data dependencies are described. For example, in accordance with one or more embodiments, a method can comprise identifying, by a device comprising a processor, in a group of dependent nodes of a cluster of nodes, a first portion of the dependent nodes for which an update is implicated. The method can further comprise selecting, by the device, from the first portion, a second portion of the dependent nodes that are predicted to be able to be updated with the update without affecting access to data of the group of dependent nodes. Further, the method can comprise communicating, by the device, the update to the second portion of the dependent nodes.

Systems for distributed data storage. A method commences upon accessing a set of data items that describe computing nodes to be organized into a ring topology. The ring topology and distributed data storage policies are characterized by quantitative failure-resilient characteristics such as a replication factor. Various characteristics of the topology serve to bound two or more availability domains of the ring into which the computing nodes can be mapped. A set of quantitative values pertaining to respective quantitative failure-resilient characteristics are used for enumerating candidate ring topologies where the computing nodes are mapped into the availability domains. Using the quantitative failure-resilient characteristics, alternative candidate ring topologies are evaluated so as to determine a configuration score for candidate ring topologies. A candidate ring topology is configured based on a computed configuration score surpassing a threshold score. When a failure event is detected, the ring is reevaluated, remapped, and considered for reconfiguration.

In general, embodiments of the invention relate to storing data and managing the stored data in linked nodes. More specifically, embodiments of the invention relate to nodes linked together in a daisy chain configuration such as, but not limited to, a single-chain configuration and a dual-chain configuration, which use data protection domain (DPD) information to determine where and/or how to store the data.

In a running distributed data storage system that actively processes I/Os, metadata nodes are commissioned and decommissioned without taking down the storage system and without introducing interruptions to metadata or payload data I/O. The inflow of reads and writes continues without interruption even while new metadata nodes are in the process of being added and/or removed and the strong consistency of the system is guaranteed. Commissioning and decommissioning nodes within the running system enables streamlined replacement of permanently failed nodes and advantageously enables the system to adapt elastically to workload changes. An illustrative distributed barrier logic (the “view change barrier”) controls a multi-state process that controls a coordinated step-wise progression of the metadata nodes from an old view to a new normal. Rules for I/O handling govern each state until the state machine loop has been traversed and the system reaches its new normal.

Systems and methods for managing a highly available distributed database comprising: a memory storing instructions; and one or more processors configured to execute the instructions to: determine that a source node, in a distributed database comprising the source node and one or more replica nodes, is not available; select a most-updated replica node from the one or more replica nodes; switch a role of the most-updated replica node to source; update a data store to label the source node as unavailable and the selected replica node as being a promoted source node; send a notification to a user device to update a database topology based on the updated data store; determine whether the user device has updated the database topology; and upon determining the user device has not updated the database topology, continue to send the notification to the user device until the user device has updated the database topology.

A computing system in data communication with a plurality of nodes that make up a distributed computing cluster can detect an absence of communication from a node of the plurality of nodes over a time period that exceeds a predefined threshold time period. The computing system can query an instance of a central topology manager for the plurality of nodes regarding liveness of the node from which the absence of communication was detected and can attempting to re-initiate communication with the node when the instance of the central topology manager indicates that the node is live.

In one embodiment, the present disclosure describes a method of optimizing memory access in a hierarchical memory system. The method includes determining a request rate from an i.sup.th layer of the hierarchical memory system for each of n layers in the hierarchical memory system. The method also includes determining a supply rate from an (i+1).sup.th layer of the hierarchical memory system for each of the n layers in the hierarchical memory system. The supply rate from the (i+1).sup.th layer of the hierarchical memory system corresponds to the request rate from the i.sup.th layer of the hierarchical memory system. The method further includes adjusting a set of computer architecture parameters of the hierarchical memory system or a schedule associated with an instruction set to utilize heterogeneous computing resources within the hierarchical memory system to match a performance of each adjacent layer of the hierarchical memory system.

Techniques for load balancing and fault tolerant service are described. An apparatus may comprise load balancing and fault tolerant component operative to execute a load balancing and fault tolerant service in a distributed data system. The load balancing and fault tolerant service distributes a load of a task to a first node in a cluster of nodes using a routing table. The load balancing and fault tolerant service stores information to indicate the first node from the cluster of nodes is assigned to perform the task. The load balancing and fault tolerant service detects a failure condition for the first node. The load balancing and fault tolerant service moves the task to a second node from the cluster of nodes to perform the task for the first node upon occurrence of the failure condition.

A method for authorizing I/O (input/output) commands in a storage cluster is provided. The method includes generating a token responsive to an I/O command, wherein the token is specific to assignment of a storage node of the storage cluster. The method includes verifying the I/O command using the token, wherein the token includes a signature confirming validity of the token and wherein the token is revocable.

A fastener cartridge for use with a surgical instrument. The cartridge may include a cartridge body that has a series of staple pockets therein. A driver is movably supported in each staple pocket and is configured to operably support at least one surgical staple thereon. In one arrangement, at least some of the drivers may be formed with one or more laterally extending features that are configured to be received in correspondingly-shaped grooves in the cartridge body to provide lateral support to the driver as it is operably moved within the staple pocket. In other arrangements, at least one inwardly-extending features is formed in the inner wall surface of the pocket and is configured to be movably supported within correspondingly-shaped groove in the driver.