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RAID, an acronym for Redundant Array of Inexpensive Disks or Redundant Array of Independent Disks, is a technology that allows high levels of storage reliability from low-cost and less reliable PC-class disk-drive components, via the technique of arranging the devices into arrays for redundancy. This concept was first defined by David A. Patterson, Garth A. Gibson, and Randy Katz at the University of California, Berkeley in 1987 as Redundant array of inexpensive disks. Marketers representing industry RAID manufacturers later reinvented the term to describe a Redundant array of independent disks as a means of dissociating a "low cost" expectation from RAID technology. RAID is now used as an umbrella term for computer data storage schemes that can divide and replicate data among multiple hard disk drives. The different schemes/architectures are named by the word RAID followed by a number, as in RAID 0, RAID 1, etc. RAID's various designs involve two key design goals: increase data reliability and/or increase input/output performance. When multiple physical disks are set up to use RAID technology, they are said to be in a RAID array. This array distributes data across multiple disks, but the array is seen by the computer user and operating system as one single disk. RAID can be set up to serve several different purposes. Both hardware and software RAIDs with redundancy may support the use of hot spare drives, a drive physically installed in the array which is inactive until an active drive fails, when the system automatically replaces the failed drive with the spare, rebuilding the array with the spare drive included. This reduces the mean time to recovery (MTTR), though it doesn't eliminate it completely. Subsequent additional failure(s) in the same RAID redundancy group before the array is fully rebuilt can result in loss of the data; rebuilding can take several hours, especially on busy systems. Rapid replacement of failed drives is important as the drives of an array will all have had the same amount of use, and may tend to fail at about the same time rather than randomly. RAID 6 without a spare uses the same number of drives as RAID 5 with a hot spare and protects data against simultaneous failure of up to two drives, but requires a more advanced RAID controller. Further, a hot spare can be shared by multiple RAID sets. [READ THE REST OF THIS ARTICLE]



The Emperor Penguin is the tallest and heaviest of all living penguin species and is endemic to Antarctica. The male and female are similar in plumage and size, reaching 122 cm in height and weighing anywhere from 22 to 45 kg. The dorsal side and head are black and sharply delineated from the white belly, pale-yellow breast and bright-yellow ear patches. Like all penguins it is flightless, with a streamlined body, and wings stiffened and flattened into flippers for a marine habitat. Its diet consists primarily of fish, but can also include crustaceans, such as krill, and cephalopods, such as squid. In hunting, the species can remain submerged up to 18 minutes, diving to a depth of 535 m. It has several adaptations to facilitate this, including an unusually structured hemoglobin to allow it to function at low oxygen levels, solid bones to reduce barotrauma, and the ability to reduce its metabolism and shut down non-essential organ functions. The Emperor Penguin is perhaps best known for the sequence of journeys adults make each year in order to mate and to feed their offspring. The only penguin species that breeds during the Antarctic winter, it treks 50–120 km over the ice to breeding colonies which may include thousands of individuals. The female lays a single egg, which is incubated by the male while the female returns to the sea to forage; parents subsequently take turns foraging at sea and caring for their chick in the colony. The lifespan is typically 20 years in the wild, although observations suggest that some individuals may live to 50 years of age. In addition to the cold, the Emperor Penguin encounters another stressful condition on deep dives—markedly increased pressure of up to 40 times that of the surface, which in most other terrestrial organisms would cause barotrauma. The bones of the penguin are solid rather than air-filled, which eliminates the risk of mechanical barotrauma. In 2012 the Emperor Penguin was uplisted from a species of least concern to near threatened by the IUCN. Along with nine other species of penguin, it is currently under consideration for inclusion under the US Endangered Species Act. The primary reasons for this are declining food availability due to the effects of climate change and industrial fisheries on the crustacean and fish populations. Other reasons for their potential placement on this list include disease, habitat destruction, and disturbance at breeding colonies by humans. [READ THE REST OF THIS ARTICLE]





The Greensboro sit-ins were a series of nonviolent protests which led to the Woolworth's department store chain reversing its policy of racial segregation in the Southern United States. While not the first sit-ins of the African-American Civil Rights Movement, the Greensboro sit-ins were an instrumental action, leading to increased national sentiment at a crucial period in American history. The primary event took place at the Greensboro, North Carolina Woolworth's store, now the International Civil Rights Center and Museum. The sit-in movement used the strategy of nonviolent resistance. As far back as 1942, the Congress of Racial Equality sponsored sit-ins in Chicago, as they did in St. Louis in 1949 and Baltimore in 1952. In August, 1939, African-American attorney Samuel Wilbert Tucker organized a sit-in at the then-segregated Alexandria, Virginia library. On February 1, 1960, four students from the Agricultural and Technical College of North Carolina sat down at the lunch counter inside the Woolworth's store in Greensboro, North Carolina. The men, later known as the Greensboro Four, ordered coffee. Following store policy, the lunch counter staff refused to serve the African American men at the "whites only" counter and the store's manager asked them to leave. The four university freshmen -- Joseph McNeil, Franklin McCain, Ezell Blair, Jr. (later known as Jibreel Khazan), and David Richmond -- stayed until the store closed. The next day, more than twenty African American students who had been recruited from other campus groups came to the store to join the sit-in. White customers heckled the black students, who read books and studied to keep busy. The lunch counter staff continued to refuse service. Newspaper reporters and a TV videographer covered the second day of peaceful demonstrations and others in the community learned of the protests. On the third day, more than 60 people came to the Woolworth's store. A statement issued by Woolworth's national headquarters said the company would "abide by local custom" and maintain its segregated policy. The movement then spread to other Southern cities including Richmond, Virginia, and Nashville, Tennessee where the students of the Nashville Student Movement had been trained for a sit-in by civil rights activist James Lawson and had already started the process when Greensboro occurred. Although the majority of these protests were peaceful, there were instances where protests became violent. For example, in Chattanooga, Tennessee, tensions rose between blacks and whites and fights broke out. As the sit-ins continued, tensions grew in Greensboro and students began a far-reaching boycott of stores that had segregated lunch counters. Sales at the boycotted stores dropped by a third, leading the stores' owners to abandon their segregation policies. Black employees of Greensboro’s Woolworth’s store were the first to be served at the store's lunch counter, on July 25, 1960. The next day, the entire Woolworth's chain was desegregated, serving blacks and whites alike. [READ THE REST OF THIS ARTICLE]



Bladesmithing is the art of making knives, swords, daggers and other blades using a forge, hammer, anvil, and other smithing tools. Bladesmiths employ a variety of metalworking techniques similar to those used by blacksmiths, as well as woodworking for knife and sword handles, and often leatherworking for sheaths. Bladesmithing is an art that is thousands of years old and found in cultures as diverse as China, Japan, India, Germany, Korea, the Middle East, and the British Isles. As with any art shrouded in history, there are myths and misconceptions about the process. While traditionally, bladesmithing referred to the manufacture of any blade by any means, the majority of contemporary craftsmen referred to as bladesmiths are those who primarily manufacture blades by means of using a forge to shape the blade as opposed to knifemakers who form blades by use of the stock removal method, although there is some overlap between both crafts. Historically speaking, bladesmithing is an art that has survived and thrived over thousands of years. Many different parts of the world have different styles of bladesmithing, some more well-known than others. The Proto-Celtic Hallstatt culture (8th century BC) were among the earliest users of iron swords. During the Hallstatt period, they made swords both in bronze as well as iron with rounded tips. Toward the end of the Hallstatt period, around 600-500BC, these swords were replaced with short daggers. The La Tene culture reintroduced the sword, which were very different from the traditional shape and construction of the Bronze Age and early Iron Age, characterized by a more pointed tip. Bladesmithing began declining after the Industrial Revolution. With improvements in steel production, bladesmiths no longer had to forge steel and knives could be machined from flat bars of steel. As cutlery companies moved to mass production of blades and machine tools became more available, the art of forging steel began to disappear as knifemakers could grind blades out of existing stock. By the mid 20th century, bladesmithing had been relegated to a cottage industry carried out by a handful of bladesmiths. One of these bladesmiths was William F. Moran, who forged his knives using a coal forge in the manner of a blacksmith using a hammer and anvil to shape the steel. Moran began trying to revive the ancient process of forging Damascus steel in the late 1960s. However, no living bladesmith knew the exact techniques and without a recipe for the process, it was in danger of being lost; through trial and error he taught himself pattern welding and referred to his end product as "Damascus steel". [READ THE REST OF THIS ARTICLE]



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