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Disk Array Controller
A disk array controller is a device that manages the physical disk drives and presents them to the computer as logical units. It often implements hardware RAID, thus it is sometimes referred to as RAID controller. It also often provides additional disk cache. ''Disk array controller'' is often ambiguously shortened to ''disk controller'' which can also refer to the circuitry responsible for managing internal disk drive operations. Front-end and back-end side A disk array controller provides front-end interfaces and back-end interfaces. * The back-end interface communicates with the controlled disks. Hence, its protocol is usually ATA (a.k.a. PATA), SATA, SCSI, FC or SAS. * The front-end interface communicates with a computer's host adapter (HBA, Host Bus Adapter) and uses: ** one of ATA, SATA, SCSI, FC; these are popular protocols used by disks, so by using one of them a controller may transparently emulate a disk for a computer. ** somewhat less popular dedicated protoc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Disk Drives
Data storage is the recording (storing) of information (data) in a storage medium. Handwriting, phonographic recording, magnetic tape, and optical discs are all examples of storage media. Biological molecules such as RNA and DNA are considered by some as data storage. Recording may be accomplished with virtually any form of energy. Electronic data storage requires electrical power to store and retrieve data. Data storage in a digital, machine-readable medium is sometimes called ''digital data''. Computer data storage is one of the core functions of a general-purpose computer. Electronic documents can be stored in much less space than paper documents. Barcodes and magnetic ink character recognition (MICR) are two ways of recording machine-readable data on paper. Recording media A recording medium is a physical material that holds information. Newly created information is distributed and can be stored in four storage media–print, film, magnetic, and optical–and seen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
InfiniBand
InfiniBand (IB) is a computer networking communications standard used in high-performance computing that features very high throughput and very low latency. It is used for data interconnect both among and within computers. InfiniBand is also used as either a direct or switched interconnect between servers and storage systems, as well as an interconnect between storage systems. It is designed to be scalable and uses a switched fabric network topology. Between 2014 and June 2016, it was the most commonly used interconnect in the TOP500 list of supercomputers. Mellanox (acquired by Nvidia) manufactures InfiniBand host bus adapters and network switches, which are used by large computer system and database vendors in their product lines. As a computer cluster interconnect, IB competes with Ethernet, Fibre Channel, and Intel Omni-Path. The technology is promoted by the InfiniBand Trade Association. History InfiniBand originated in 1999 from the merger of two competing designs: ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PCIe
PCI Express (Peripheral Component Interconnect Express), officially abbreviated as PCIe, is a high-speed standard used to connect hardware components inside computers. It is designed to replace older expansion bus standards such as Peripheral Component Interconnect, PCI, PCI-X and Accelerated Graphics Port, AGP. Developed and maintained by the PCI-SIG (PCI Special Interest Group), PCIe is commonly used to connect graphics cards, sound cards, Wi-Fi and Ethernet adapters, and storage devices such as solid-state drives and hard disk drives. Compared to earlier standards, PCIe supports faster data transfer, uses fewer pins, takes up less space, and allows devices to be added or removed while the computer is running (hot swapping). It also includes better error detection and supports newer features like I/O virtualization for advanced computing needs. PCIe connections are made through "lanes," which are pairs of wires that send and receive data. Devices can use one or more lanes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Peripheral Component Interconnect
Peripheral Component Interconnect (PCI) is a local computer bus for attaching hardware devices in a computer and is part of the PCI Local Bus standard. The PCI bus supports the functions found on a processor bus but in a standardized format that is independent of any given processor's native bus. Devices connected to the PCI bus appear to a bus master to be connected directly to its own bus and are assigned addresses in the processor's address space. It is a parallel bus, synchronous to a single bus clock. Attached devices can take either the form of an integrated circuit fitted onto the motherboard (called a ''planar device'' in the PCI specification) or an expansion card that fits into a slot. The PCI Local Bus was first implemented in IBM PC compatibles, where it displaced the combination of several slow Industry Standard Architecture (ISA) slots and one fast VESA Local Bus (VLB) slot as the bus configuration. It has subsequently been adopted for other computer types ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Promise Ultra33
A promise is a commitment by someone to do or not do something. As a noun ''promise'' means a declaration assuring that one will or will not do something. As a verb it means to commit oneself by a promise to do or give. It can also mean a capacity for good, similar to a value that is to be realized in the near future. In the law of contract, an exchange of promises is usually held to be legally enforceable, according to the Latin maxim ''pacta sunt servanda''. Types There are many types of promises. There are solemn promises, such as marriage vows or military oaths and are conventions. There are legal contracts, enforceable by law. Or, there are fairy tale promises, regrettable and problematic at the time, they must be honored. And lastly, there are election promises, commitments that most people realize will later be shaped by politics and compromise. Both an oath and an affirmation can be a promise. One special kind of promise is the vow. A notable type of promise is an ele ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Disk Mirroring
In Data storage device, data storage, disk mirroring is the Replication (computing), replication of logical disk volumes onto separate physical hard disks in Real-time computing, real time to ensure continuous availability. It is most commonly used in RAID 1. A mirrored volume is a complete logical representation of separate volume copies. In a IT disaster recovery, disaster recovery context, mirroring data over long distance is referred to as storage replication. Depending on the technologies used, replication can be performed synchronously, Asynchronous communication, asynchronously, semi-synchronously, or point-in-time. Replication is enabled via microcode on the disk array controller or via Server (computing), server software. It is typically a proprietary solution, not compatible between various data storage device vendors. Mirroring is typically only synchronous. Synchronous writing typically achieves a recovery point objective (RPO) of zero lost data. Asynchronous replica ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Business Continuance Volume
In disk arrays, a business continuance volume (BCV) is EMC Corporation's term for an independently addressable copy of a data volume, that uses advanced mirroring technique for business continuity purposes. Use BCVs can be detached from the active data storage at a point in time and mounted on non-critical servers to facilitate offline backup or parallel computing. Once offline processes are completed, these BCVs can be either: * discarded * used as a source to recover the production data * re-attached (re-synchronized) to the production data again Types There are two types of BCVs: * A clone BCV is a traditional method, and uses one-to-one separate physical storage (splitable disk mirror) ** least impact on production performance ** high cost of the additional storage ** persistent usage * A snapshot BCV, that uses copy on write Copy may refer to: *Copying or the product of copying (including the plural "copies"); the duplication of information or an artifact **Cut, co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Snapshot (computer Storage)
In Computer, computer systems, a snapshot is the State (computer science), state of a system at a particular point in time. The term was coined as an analogy to that in Snapshot (photography), photography. Rationale A full backup of a large data set may take a long time to complete. On Computer multitasking, multi-tasking or multi-user systems, there may be writes to that data while it is being backed up. This prevents the backup from being Atomicity (database systems), atomic and introduces a version skew that may result in data corruption. For example, if a user moves a file into a directory that has already been backed up, then that file would be completely missing on the Computer data storage, backup media, since the backup operation had already taken place before the addition of the file. Version skew may also cause corruption with files which change their size or contents underfoot while being read. One Backup#Approaches to backing up live data, approach to safely backin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Downtime
In computing and telecommunications, downtime (also (system) outage or (system) drought colloquially) is a period when a system is unavailable. The unavailability is the proportion of a time-span that a system is unavailable or offline. This is usually a result of the system failing to function because of an unplanned event, or because of routine maintenance (a planned event). The terms are commonly applied to networks and servers. The common reasons for unplanned outages are system failures (such as a crash) or communications failures (commonly known as network outage or network drought colloquially). For outages due to issues with general computer systems, the term computer outage (also IT outage or IT drought) can be used. The term is also commonly applied in industrial environments in relation to failures in industrial production equipment. Some facilities measure the downtime incurred during a work shift, or during a 12- or 24-hour period. Another common practice is to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Failover
Failover is switching to a redundant or standby computer server, system, hardware component or network upon the failure or abnormal termination of the previously active application, server, system, hardware component, or network in a computer network. Failover and switchover are essentially the same operation, except that failover is automatic and usually operates without warning, while switchover requires human intervention. History The term "failover", although probably in use by engineers much earlier, can be found in a 1962 declassified NASA report. The term "switchover" can be found in the 1950s when describing '"Hot" and "Cold" Standby Systems', with the current meaning of immediate switchover to a running system (hot) and delayed switchover to a system that needs starting (cold). A conference proceedings from 1957 describes computer systems with both Emergency Switchover (i.e. failover) and Scheduled Failover (for maintenance). Failover Systems designers usually pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Server (computing)
A server is a computer that provides information to other computers called " clients" on a computer network. This architecture is called the client–server model. Servers can provide various functionalities, often called "services", such as sharing data or resources among multiple clients or performing computations for a client. A single server can serve multiple clients, and a single client can use multiple servers. A client process may run on the same device or may connect over a network to a server on a different device. Typical servers are database servers, file servers, mail servers, print servers, web servers, game servers, and application servers. Client–server systems are usually most frequently implemented by (and often identified with) the request–response model: a client sends a request to the server, which performs some action and sends a response back to the client, typically with a result or acknowledgment. Designating a computer as "server-class hardwa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Network-attached Storage
Network-attached storage (NAS) is a file-level computer data storage server connected to a computer network providing data access to a Heterogeneous computing, heterogeneous group of clients. In this context, the term "NAS" can refer to both the technology and systems involved, or a specialized computer appliance device unit built for such functionality – a ''NAS appliance'' or ''NAS box''. NAS contrasts with block-level storage, block-level storage area networks (SAN). Overview A NAS device is optimised for file server, serving files either by its hardware, software, or configuration. It is often manufactured as a computer appliance a purpose-built specialized computer. NAS systems are networked appliances that contain one or more hard disk drive, storage drives, often arranged into logical disk, logical, redundant storage containers or RAID. Network-attached storage typically provide access to files using network file sharing protocols such as Network File System (protocol), ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
