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Split-brain (computing)
Split-brain is a computer term, based on an analogy with the medical split-brain syndrome. It indicates data or availability inconsistencies originating from the maintenance of two separate data sets with overlap in scope, either because of servers in a network design, or a failure condition based on servers not communicating and synchronizing their data to each other. This last case is also commonly referred to as a network partition. Although the term split-brain typically refers to an error state, split-brain DNS (or split-horizon DNS) is sometimes used to describe a deliberate situation where internal and external DNS services for a corporate network are not communicating, so that separate DNS name spaces are to be administered for external computers and for internal ones. This requires a double administration, and if there is domain overlap in the computer names, there is a risk that the same fully qualified domain name (FQDN), may ambiguously occur in both name spaces refe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Split-brain
Split-brain or callosal syndrome is a type of disconnection syndrome when the corpus callosum connecting the two hemispheres of the brain is severed to some degree. It is an association of symptoms produced by disruption of, or interference with, the connection between the hemispheres of the brain. The surgical operation to produce this condition ( corpus callosotomy) involves transection of the corpus callosum, and is usually a last resort to treat refractory epilepsy. Initially, partial callosotomies are performed; if this operation does not succeed, a complete callosotomy is performed to mitigate the risk of accidental physical injury by reducing the severity and violence of epileptic seizures. Before using callosotomies, epilepsy is instead treated through pharmaceutical means. After surgery, neuropsychological assessments are often performed. After the right and left brain are separated, each hemisphere will have its own separate perception, concepts, and impulses to act ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Network Planning And Design
Network planning and design is an iterative process, encompassing #A network planning methodology, topological design, #A network planning methodology, network-synthesis, and #A network planning methodology, network-realization, and is aimed at ensuring that a new telecommunications network or service meets the needs of the subscriber and network operator, operator.Penttinen A., ''Chapter 10 – Network Planning and Dimensioning, Lecture Notes: S-38.145 - Introduction to Teletraffic Theory'', Helsinki University of Technology, Fall 1999. The process can be tailored according to each new network or service.Farr R.E., ''Telecommunications Traffic, Tariffs and Costs – An Introduction For Managers'', Peter Peregrinus Ltd, 1988. A network planning methodology A traditional network planning methodology in the context of business decisions involves five layers of planning, namely: * need assessment and resource assessment * short-term network planning * IT resource * long-term and m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Network Partition
A network partition is a division of a computer network into relatively independent subnets, either by design, to optimize them separately, or due to the failure of network devices. Distributed software must be designed to be partition-tolerant, that is, even after the network is partitioned, it still works correctly. For example, in a network with multiple subnets where nodes A and B are located in one subnet and nodes C and D are in another, a partition occurs if the network switch device between the two subnets fails. In that case nodes A and B can no longer communicate with nodes C and D, but all nodes A-D work the same as before. As a CAP trade-off The CAP theorem is based on three trade-offs: consistency, availability, and partition tolerance. Partition tolerance, in this context, means the ability of a data processing system to continue processing data even if a network partition causes communication errors between subsystems. External links Partition of the Large ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Split-horizon DNS
In computer networking, split-horizon DNS (also known as split-view DNS, split-brain DNS, or split DNS, or Mirage) is the facility of a Domain Name System (DNS) implementation to provide different sets of DNS information, usually selected by the source address of the DNS request. This facility can provide a mechanism for security and privacy management by logical or physical separation of DNS information for network-internal access (within an administrative domain, e.g., company) and access from an unsecure, public network (e.g. the Internet). Implementation of split-horizon DNS can be accomplished with hardware-based separation or by software. Hardware-based implementations run distinct DNS server devices for the desired access granularity within the networks involved. Software solutions use either multiple DNS server processes on the same hardware or special server software with the built-in capability of discriminating access to DNS zone records. The latter is a common feature ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Domain Name System
The Domain Name System (DNS) is a hierarchical and distributed name service that provides a naming system for computers, services, and other resources on the Internet or other Internet Protocol (IP) networks. It associates various information with ''domain names'' (identification (information), identification String (computer science), strings) assigned to each of the associated entities. Most prominently, it translates readily memorized domain names to the numerical IP addresses needed for locating and identifying computer services and devices with the underlying network protocols. The Domain Name System has been an essential component of the functionality of the Internet since 1985. The Domain Name System delegates the responsibility of assigning domain names and mapping those names to Internet resources by designating authoritative name servers for each domain. Network administrators may delegate authority over subdomains of their allocated name space to other name servers. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fully Qualified Domain Name
A fully qualified domain name (FQDN), sometimes also called an absolute domain name, is a domain name that specifies its exact location in the tree hierarchy of the Domain Name System (DNS). It specifies all domain levels, including the top-level domain and the root zone. A fully qualified domain name is distinguished by its unambiguous DNS zone location in the hierarchy of DNS labels: it can be interpreted only in one way. Definition A fully qualified domain name is conventionally written as a list of domain labels separated using the full stop "" character (''dot'' or ''period''). The top of the hierarchy in an FQDN begins with the rightmost label. For instance, in the FQDN , is a label directly under the root zone, is nested under , and finally is nested under . The topmost layer of every domain name is the DNS root zone, which is expressed as an empty label and can be represented in an FQDN with a trailing dot, such as . A trailing dot is generally implied and often om ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
High-availability Cluster
In computing, high-availability clusters (HA clusters) or fail-over clusters are groups of computers that support server applications that can be reliably utilized with a minimum amount of down-time. They operate by using high availability software to harness redundant computers in groups or clusters that provide continued service when system components fail. Without clustering, if a server running a particular application crashes, the application will be unavailable until the crashed server is fixed. HA clustering remedies this situation by detecting hardware/software faults, and immediately restarting the application on another system without requiring administrative intervention, a process known as failover. As part of this process, clustering software may configure the node before starting the application on it. For example, appropriate file systems may need to be imported and mounted, network hardware may have to be configured, and some supporting applications may nee ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heartbeat Private Network
In computer science, a heartbeat is a periodic signal generated by hardware or software to indicate normal operation or to synchronize other parts of a computer system. Heartbeat mechanism is one of the common techniques in mission critical systems for providing high availability and fault tolerance of network services by detecting the network or systems failures of nodes or daemons which belongs to a network cluster—administered by a master server—for the purpose of automatic adaptation and rebalancing of the system by using the remaining redundant nodes on the cluster to take over the load of failed nodes for providing constant services. Usually a heartbeat is sent between machines at a regular interval in the order of seconds; a heartbeat message. If the endpoint does not receive a heartbeat for a time—usually a few heartbeat intervals—the machine that should have sent the heartbeat is assumed to have failed. Heartbeat messages are typically sent non-stop on a per ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data Corruption
Data corruption refers to errors in computer data that occur during writing, reading, storage, transmission, or processing, which introduce unintended changes to the original data. Computer, transmission, and storage systems use a number of measures to provide end-to-end data integrity, or lack of errors. In general, when data corruption occurs, a Computer file, file containing that data will produce unexpected results when accessed by the system or the related application. Results could range from a minor loss of data to a system crash. For example, if a Document file format, document file is corrupted, when a person tries to open that file with a document editor they may get an error message, thus the file might not be opened or might open with some of the data corrupted (or in some cases, completely corrupted, leaving the document unintelligible). The adjacent image is a corrupted image file in which most of the information has been lost. Some types of malware may intentional ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hazelcast
In computing, Hazelcast is a unified real-time data platform implemented in Java that combines a fast data store with stream processing. It is also the name of the company that develops the product. The Hazelcast company is funded by venture capital and headquartered in Palo Alto, California. In a Hazelcast grid, data is evenly distributed among the nodes of a computer cluster, allowing for horizontal scaling of processing and available storage. Backups are also distributed among nodes to protect against failure of any single node. Hazelcast can run on-premises, in the cloud (Amazon Web Services, Microsoft Azure, Cloud Foundry, OpenShift), virtually ( VMware), and in Docker containers. The Hazelcast Cloud Discovery Service Provider Interface (SPI) enables cloud-based or on-premises nodes to auto-discover each other. The Hazelcast platform can manage memory for many types of applications. It offers an Open Binary Client Protocol to support APIs for any binary programming ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quorum (distributed Computing)
A quorum is the minimum number of votes that a distributed transaction has to obtain in order to be allowed to perform an operation in a distributed system. A quorum-based technique is implemented to enforce consistent operation in a distributed system. Quorum-based techniques in distributed database systems Quorum-based voting can be used as a replica control method, as well as a commit method to ensure transaction atomicity in the presence of network partitioning. Quorum-based voting in commit protocols In a distributed database system, a transaction could execute its operations at multiple sites. Since atomicity requires every distributed transaction to be atomic, the transaction must have the same fate ( commit or abort) at every site. In case of network partitioning, sites are partitioned and the partitions may not be able to communicate with each other. This is where a quorum-based technique comes in. The fundamental idea is that a transaction is executed if the major ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fencing (computing)
Fencing is the process of isolating a node of a computer cluster or protecting shared resources when a node appears to be malfunctioning.''Sun Cluster environment: Sun Cluster 2.2'' by Enrique Vargas, Joseph Bianco, David Deeths 2001 ISBN page 58 As the number of nodes in a cluster increases, so does the likelihood that one of them may fail at some point. The failed node may have control over shared resources that need to be reclaimed and if the node is acting erratically, the rest of the system needs to be protected. Fencing may thus either disable the node, or disallow shared storage access, thus ensuring data integrity. Basic concepts A node fence (or I/O fence) is a virtual "fence" that separates nodes which must not have access to a shared resource from that resource. It may separate an active node from its backup. If the backup crosses the fence and, for example, tries to control the same disk array as the primary, a data hazard may occur. Mechanisms such as STONITH are de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
