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Disk Mirroring
In data storage, disk mirroring is the replication of logical disk volumes onto separate physical hard disks in 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 disaster recovery context, mirroring data over long distance is referred to as storage replication. Depending on the technologies used, replication can be performed synchronously, asynchronously, semi-synchronously, or point-in-time. Replication is enabled via microcode on the disk array controller or via 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 replication can achieve an RPO of just a few seconds while the remaining methodologies provide an RPO of a few minutes to perhaps severa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Raid1 Version For Wiki
In computer storage, the standard RAID levels comprise a basic set of RAID ("redundant array of independent disks" or "redundant array of inexpensive disks") configurations that employ the techniques of striping, mirroring, or parity to create large reliable data stores from multiple general-purpose computer hard disk drives (HDDs). The most common types are RAID 0 (striping), RAID 1 (mirroring) and its variants, RAID 5 (distributed parity), and RAID 6 (dual parity). Multiple RAID levels can also be combined or ''nested'', for instance RAID 10 (striping of mirrors) or RAID 01 (mirroring stripe sets). RAID levels and their associated data formats are standardized by the Storage Networking Industry Association (SNIA) in the Common RAID Disk Drive Format (DDF) standard. The numerical values only serve as identifiers and do not signify performance, reliability, generation, or any other metric. While most RAID levels can provide good protection against a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
File Shadowing
In digital file management, copying is a file operation that creates a new file which has the same content as an existing file. Computer operating systems include file copying methods to users, with operating systems with graphical user interfaces (GUIs) often providing copy-and-paste or drag-and-drop methods of file copying. Operating systems may have specialized file copying APIs are usually able to tell the server to perform the copying locally, without sending file contents over the network, thus greatly improving performance. Description File copying is the creation of a new copy file which has the same content as an existing file. Shadow There are several different technologies that use the term shadowing, but the intent of shadowing within these technologies is to provide an exact copy (or mirror of a set) of data. For shadowing to be effective, the shadow needs to exist in a separate physical location than the original data. Depending on the reasons behind the shadow ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mirror Site
Mirror sites or mirrors are replicas of other websites or any network node. The concept of mirroring applies to network services accessible through any protocol, such as HTTP or FTP. Such sites have different URLs than the original site, but host identical or near-identical content. Mirror sites are often located in a different geographic region than the original, or upstream site. The purpose of mirrors is to reduce network traffic, improve access speed, ensure availability of the original site for technical or political reasons, or provide a real-time backup of the original site. Mirror sites are particularly important in developing countries, where internet access may be slower or less reliable. The maintainers of some mirrors choose not to replicate the entire contents of the upstream server they are mirroring because of technical constraints, or selecting only a subset relevant to their purpose, such as software written in a particular programming language, runnable on a s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Distributed Replicated Block Device
DRBD is a distributed replicated storage system for the Linux platform. It is implemented as a kernel driver, several userspace management applications, and some shell scripts. DRBD is traditionally used in high availability (HA) computer clusters, but beginning with DRBD version 9, it can also be used to create larger software defined storage pools with a focus on cloud integration. A ''DRBD device'' is a ''DRBD block device'' that refers to a logical block device in a logical volume schema. The DRBD software is free software released under the terms of the GNU General Public License version 2. DRBD is part of the Lisog open source stack initiative. Mode of operation DRBD layers logical block devices (conventionally named /dev/drbd''X'', where ''X'' is the device minor number) over existing local block devices on participating cluster nodes. Writes to the ''primary'' node are transferred to the lower-level block device and simultaneously propagated to the ''secondary'' no ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Disk Cloning
Disk cloning is the process of creating a 1-to-1 copy of a hard disk drive (HDD) or solid-state drive (SSD), not just its files. Disk cloning may be used for upgrading a disk or replacing an aging disk with a fresh one. In this case, the clone can replace the original disk in its host computer. Disk cloning may also be used for disaster recovery or forensics. In the context of backup software, disk cloning is very similar to disk imaging; in case of the latter, a 1-to-1 copy of a disk is created inside a disk image file. Disk cloning may be done with specialized cloning software, backup software, disk imaging software that has the necessary features, or specialized hardware. Operating environment A disk cloning program needs to be able to read even protected operating system files on the source disk, and must guarantee that the system is in a consistent state at the time of reading. It must also overwrite any operating system already present on the destination disk. To simplify t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hot Standby
A hot spare or warm spare or hot standby is used as a failover mechanism to provide reliability in system configurations. The hot spare is active and connected as part of a working system. When a key component fails, the hot spare is switched into operation. More generally, a hot standby can be used to refer to any device or system that is held in readiness to overcome an otherwise significant start-up delay. Examples Examples of hot spares are components such as A/V switches, computers, network printers, and hard disks. The equipment is powered on, or considered "hot," but not actively functioning in (i.e. used by) the system. Electrical generators may be held on hot standby, or a steam train may be held at the shed fired up (literally hot) ready to replace a possible failure of an engine in service. Explanation In designing a reliable system, it is recognized that there will be failures. At the extreme, a complete system can be duplicated and kept up to date—so in the even ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hot Swap
Hot swapping is the replacement or addition of components to a computer system without stopping, shutting down, or rebooting the system; hot plugging describes the addition of components only. Components which have such functionality are said to be ''hot-swappable'' or ''hot-pluggable''; likewise, components which do not are ''cold-swappable'' or ''cold-pluggable''. Most desktop computer hardware, such as CPUs and memory, are only cold-pluggable. However, it is common for mid to high-end servers and mainframes to feature hot-swappable capability for hardware components, such as CPU, memory, PCIe, SATA and SAS drives. An example of hot swapping is the express ability to pull a Universal Serial Bus (USB) peripheral device, such as a thumb drive, external hard disk drive (HDD), mouse, keyboard, or printer out of a computer's USB slot or peripheral hub without ejecting it first. Most smartphones and tablets with tray-loading holders can interchange SIM cards without power ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Linux Foundation
The Linux Foundation (LF) is a non-profit technology consortium founded in 2000 as a merger between Open Source Development Labs and the Free Standards Group to standardize Linux, support its growth, and promote its commercial adoption. Additionally, it hosts and promotes the collaborative development of open source software projects. It is a major force in promoting diversity and inclusion in both Linux and the wider open source software community. The foundation was launched in 2000, under the Open Source Development Labs (OSDL) and became the organization it is today when OSDL merged with the Free Standards Group (FSG). The Linux Foundation sponsors the work of Linux creator Linus Torvalds and lead maintainer Greg Kroah-Hartman. Furthermore, it is supported by members, such as AT&T, Cisco, Fujitsu, Google, Hitachi, Huawei, IBM, Intel, Meta, Microsoft, NEC, Oracle, Orange S.A., Qualcomm, Samsung, Tencent, and VMware, as well as developers from around the world. In rece ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Btrfs
Btrfs (pronounced as "better F S", "butter F S", "b-tree F S", or simply by spelling it out) is a computer storage format that combines a file system based on the copy-on-write (COW) principle with a logical volume manager (not to be confused with Linux's LVM), developed together. It was initially designed at Oracle Corporation in 2007 for use in Linux, and since November 2013, the file system's on-disk format has been declared stable in the Linux kernel. According to Oracle, Btrfs "is not a true acronym". Btrfs is intended to address the lack of pooling, snapshots, checksums, and integral multi-device spanning in Linux file systems. Chris Mason, the principal Btrfs author, stated that its goal was "to let inuxscale for the storage that will be available. Scaling is not just about addressing the storage but also means being able to administer and to manage it with a clean interface that lets people see what's being used and makes it more reliable". History The core dat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
File System
In computing, file system or filesystem (often abbreviated to fs) is a method and data structure that the operating system uses to control how data is stored and retrieved. Without a file system, data placed in a storage medium would be one large body of data with no way to tell where one piece of data stopped and the next began, or where any piece of data was located when it was time to retrieve it. By separating the data into pieces and giving each piece a name, the data are easily isolated and identified. Taking its name from the way a paper-based data management system is named, each group of data is called a " file". The structure and logic rules used to manage the groups of data and their names is called a "file system." There are many kinds of file systems, each with unique structure and logic, properties of speed, flexibility, security, size and more. Some file systems have been designed to be used for specific applications. For example, the ISO 9660 file system is desig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Red Hat
Red Hat, Inc. is an American software company that provides open source software products to enterprises. Founded in 1993, Red Hat has its corporate headquarters in Raleigh, North Carolina, with other offices worldwide. Red Hat has become associated to a large extent with its enterprise operating system Red Hat Enterprise Linux. With the acquisition of open-source enterprise middleware vendor JBoss, Red Hat also offers Red Hat Virtualization (RHV), an enterprise virtualization product. Red Hat provides storage, operating system platforms, middleware, applications, management products, and support, training, and consulting services. Red Hat creates, maintains, and contributes to many free software projects. It has acquired several proprietary software product codebases through corporate mergers and acquisitions and has released such software under open source licenses. , Red Hat is the second largest corporate contributor to the Linux kernel version 4.14 after Intel. On Oc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Device Mapper
The device mapper is a framework provided by the Linux kernel for mapping physical block devices onto higher-level ''virtual block devices''. It forms the foundation of the logical volume manager (LVM), software RAIDs and dm-crypt disk encryption, and offers additional features such as file system snapshots. Device mapper works by passing data from a virtual block device, which is provided by the device mapper itself, to another block device. Data can be also modified in transition, which is performed, for example, in the case of device mapper providing disk encryption or simulation of unreliable hardware behavior. This article focuses on the device mapper implementation in the Linux kernel, but the device mapper functionality is also available in both NetBSD and DragonFly BSD. Usage Applications (like LVM2 and Enterprise Volume Management System (EVMS)) that need to create new mapped devices talk to the device mapper via the libdevmapper.so shared library, which in turn iss ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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