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RAID
RAID (; redundant array of inexpensive disks or redundant array of independent disks) is a data storage virtualization technology that combines multiple physical Computer data storage, data storage components into one or more logical units for the purposes of data redundancy, performance improvement, or both. This is in contrast to the previous concept of highly reliable mainframe disk drives known as ''single large expensive disk'' (''SLED''). Data is distributed across the drives in one of several ways, referred to as RAID levels, depending on the required level of redundancy (engineering), redundancy and performance. The different schemes, or data distribution layouts, are named by the word "RAID" followed by a number, for example RAID 0 or RAID 1. Each scheme, or RAID level, provides a different balance among the key goals: reliability engineering, reliability, availability, computer performance, performance, and computer data storage#Capacity, capacity. RAID levels ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nested RAID Levels
Nested RAID levels, also known as hybrid RAID, combine two or more of the standard RAID levels (where "RAID" stands for "redundant array of independent disks" or "redundant array of inexpensive disks") to gain performance, additional redundancy or both, as a result of combining properties of different standard RAID layouts. Nested RAID levels are usually numbered using a series of numbers, where the most commonly used levels use two numbers. The first number in the numeric designation denotes the lowest RAID level in the "stack", while the rightmost one denotes the highest layered RAID level; for example, RAID 50 layers the data striping of RAID 0 on top of the distributed parity of RAID 5. Nested RAID levels include RAID 01, RAID 10, RAID 100, RAID 50 and RAID 60, which all combine data striping with other RAID techniques; as a result of the layering scheme, RAID 01 and RAID 10 represent significantly different nested RAID levels ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RAID Levels
A RAID level is any of the possible configurations of a RAID disk array. ''RAID'' stands for ''redundant array of independent disks'' (or, formerly, ''redundant array of inexpensive disks''). RAID levels may refer to: * Standard RAID levels, all the RAID configurations defined in the Common RAID Disk Drive Format standard, which is maintained by the Storage Networking Industry Association * Nested RAID levels Nested RAID levels, also known as hybrid RAID, combine two or more of the standard RAID levels (where "RAID" stands for "redundant array of independent disks" or "redundant array of inexpensive disks") to gain performance, additional redundancy or ..., RAID configurations that incorporate features of two or more standard RAID levels * Non-standard RAID levels, variants of standard or nested RAID levels. Non-standard RAID levels deviate from the standard configurations defined by the Storage Networking Industry Association (SNIA). See also * Non-RAID drive architectures { ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Data Storage
Computer data storage or digital data storage is a technology consisting of computer components and Data storage, recording media that are used to retain digital data. It is a core function and fundamental component of computers. The central processing unit (CPU) of a computer is what manipulates data by performing computations. In practice, almost all computers use a storage hierarchy, which puts fast but expensive and small storage options close to the CPU and slower but less expensive and larger options further away. Generally, the fast technologies are referred to as "memory", while slower persistent technologies are referred to as "storage". Even the first computer designs, Charles Babbage's Analytical Engine and Percy Ludgate's Analytical Machine, clearly distinguished between processing and memory (Babbage stored numbers as rotations of gears, while Ludgate stored numbers as displacements of rods in shuttles). This distinction was extended in the Von Neumann archite ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parity Bit
A parity bit, or check bit, is a bit added to a string of binary code. Parity bits are a simple form of error detecting code. Parity bits are generally applied to the smallest units of a communication protocol, typically 8-bit octets (bytes), although they can also be applied separately to an entire message string of bits. The parity bit ensures that the total number of 1-bits in the string is even or odd. Accordingly, there are two variants of parity bits: even parity bit and odd parity bit. In the case of even parity, for a given set of bits, the bits whose value is 1 are counted. If that count is odd, the parity bit value is set to 1, making the total count of occurrences of 1s in the whole set (including the parity bit) an even number. If the count of 1s in a given set of bits is already even, the parity bit's value is 0. In the case of odd parity, the coding is reversed. For a given set of bits, if the count of bits with a value of 1 is even, the parity bit value is se ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Data Storage
Computer data storage or digital data storage is a technology consisting of computer components and Data storage, recording media that are used to retain digital data. It is a core function and fundamental component of computers. The central processing unit (CPU) of a computer is what manipulates data by performing computations. In practice, almost all computers use a storage hierarchy, which puts fast but expensive and small storage options close to the CPU and slower but less expensive and larger options further away. Generally, the fast technologies are referred to as "memory", while slower persistent technologies are referred to as "storage". Even the first computer designs, Charles Babbage's Analytical Engine and Percy Ludgate's Analytical Machine, clearly distinguished between processing and memory (Babbage stored numbers as rotations of gears, while Ludgate stored numbers as displacements of rods in shuttles). This distinction was extended in the Von Neumann archite ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adaptec
Adaptec, Inc., was a computer storage company and remains a brand for computer storage products. The company was an independent firm from 1981 to 2010, at which point it was acquired by PMC-Sierra, which itself was later acquired by Microsemi, which itself was later acquired by Microchip Technology. History Larry Boucher, Wayne Higashi, and Bernard Nieman founded Adaptec in 1981. At first, Adaptec focused on devices with Parallel SCSI interfaces. Popular host bus adapters included the 154x/15xx ISA family, the 2940 PCI family, and the 29160/-320 family. Their cross-platform ASPI was an early API for accessing and integrating non- disk devices like tape drives, scanners and optical disks. With advancements in technology, RAID functions were added while interfaces evolved to PCIe and SAS. Adaptec made a number of acquisitions in the 1990s to expand their reach in the SCSI peripheral market. In March 1993, they acquired Trantor Systems Ltd. of Fremont, California, for $ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DataVault
The DataVault was Thinking Machines' mass storage system, storing 5 GB of data, expandable to 10 GB with transfer rates of 40 MB/s. Eight DataVaults could be operated in parallel for a combined data transfer rate of 320 MB/s for up to 80 GB of data. Each DataVault unit stored its data in an array of 39 individual disk drives with data spread across the drives. Each 64-bit data chunk received from the I/O bus was split into two 32-bit words. After verifying parity, the DataVault controller added 7 bits of Error Correcting Code (ECC) and stored the resulting 39 bits on 39 individual drives. Subsequent failure of any one of the 39 drives would not impair reading of the data, since the ECC code allows any single-bit error to be detected and corrected. Although operation is possible with a single failed drive, three spare drives were available to replace failed units until they are repaired. The ECC codes permit 100% recovery of the data on any one failed disk, allowing a new copy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
David Patterson (computer Scientist)
David Andrew Patterson (born November 16, 1947) is an American computer scientist and academic who has held the position of professor of computer science at the University of California, Berkeley since 1976. He is a computer pioneer. He announced retirement in 2016 after serving nearly forty years, becoming a distinguished software engineer at Google. He currently is vice chair of the board of directors of the RISC-V Foundation, and the Pardee Professor of Computer Science, Emeritus at UC Berkeley. Patterson is noted for his pioneering contributions to reduced instruction set computer (RISC) design, having coined the term RISC, and by leading the Berkeley RISC project. As of 2018, 99% of all new chips use a RISC architecture. He is also noted for leading the research on redundant arrays of inexpensive disks (RAID) storage, with Randy Katz. His books on computer architecture, co-authored with John L. Hennessy, are widely used in computer science education. Hennessy and Patter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fault Tolerance
Fault tolerance is the ability of a system to maintain proper operation despite failures or faults in one or more of its components. This capability is essential for high-availability, mission-critical, or even life-critical systems. Fault tolerance specifically refers to a system's capability to handle faults without any degradation or downtime. In the event of an error, end-users remain unaware of any issues. Conversely, a system that experiences errors with some interruption in service or graceful degradation of performance is termed 'resilient'. In resilience, the system adapts to the error, maintaining service but acknowledging a certain impact on performance. Typically, fault tolerance describes computer systems, ensuring the overall system remains functional despite hardware or software issues. Non-computing examples include structures that retain their integrity despite damage from fatigue, corrosion or impact. History The first known fault-tolerant computer was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solid-state Drive
A solid-state drive (SSD) is a type of solid-state storage device that uses integrated circuits to store data persistently. It is sometimes called semiconductor storage device, solid-state device, or solid-state disk. SSDs rely on non-volatile memory, typically NAND flash, to store data in memory cells. The performance and endurance of SSDs vary depending on the number of bits stored per cell, ranging from high-performing single-level cells (SLC) to more affordable but slower quad-level cells (QLC). In addition to flash-based SSDs, other technologies such as 3D XPoint offer faster speeds and higher endurance through different data storage mechanisms. Unlike traditional hard disk drives (HDDs), SSDs have no moving parts, allowing them to deliver faster data access speeds, reduced latency, increased resistance to physical shock, lower power consumption, and silent operation. Often interfaced to a system in the same way as HDDs, SSDs are used in a variety of devices, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exclusive Or
Exclusive or, exclusive disjunction, exclusive alternation, logical non-equivalence, or logical inequality is a logical operator whose negation is the logical biconditional. With two inputs, XOR is true if and only if the inputs differ (one is true, one is false). With multiple inputs, XOR is true if and only if the number of true inputs is odd. It gains the name "exclusive or" because the meaning of "or" is ambiguous when both operands are true. XOR ''excludes'' that case. Some informal ways of describing XOR are "one or the other but not both", "either one or the other", and "A or B, but not A and B". It is symbolized by the prefix operator J Translated as and by the infix operators XOR (, , or ), EOR, EXOR, \dot, \overline, \underline, , \oplus, \nleftrightarrow, and \not\equiv. Definition The truth table of A\nleftrightarrow B shows that it outputs true whenever the inputs differ: Equivalences, elimination, and introduction Exclusive disjunction essentially ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Digital Equipment Corporation
Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president until he was forced to resign in 1992, after the company had gone into precipitous decline. The company produced many different product lines over its history. It is best known for the work in the minicomputer market starting in the early 1960s. The company produced a series of machines known as the Programmed Data Processor, PDP line, with the PDP-8 and PDP-11 being among the most successful minis in history. Their success was only surpassed by another DEC product, the late-1970s VAX "supermini" systems that were designed to replace the PDP-11. Although a number of competitors had successfully competed with Digital through the 1970s, the VAX cemented the company's place as a leading vendor in the computer space. As microcomputers improved in t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
