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Web Hosting - Redundancy and Failover
Among the more useful innovations in computing, actually invented decades ago, are the twin ideas of redundancy and failover. These fancy words name very common sense concepts. When one computer (or part) fails, switch to another. Doing that seamlessly and quickly versus slowly with disruption defines one difference between good hosting and bad.
Network redundancy is the most widely used example. The Internet is just that, an inter-connected set of networks. Between and within networks are paths that make possible page requests, file transfers and data movement from one spot (called a 'node') to the next. If you have two or more paths between a user's computer and the server, one becoming unavailable is not much of a problem. Closing one street is not so bad, if you can drive down another just as easily.
Of course, there's the catch: 'just as easily'. When one path fails, the total load (the amount of data requested and by how many within what time frame) doesn't change. Now the same number of 'cars' are using fewer 'roads'. That can lead to traffic jams.
A very different, but related, phenomenon occurs when there suddenly become more 'cars', as happens in a massively widespread virus attack, for example. Then, a large number of useless and destructive programs are running around flooding the network. Making the situation worse, at a certain point, parts of the networks may shut down to prevent further spread, producing more 'cars' on now-fewer 'roads'.
A related form of redundancy and failover can be carried out with servers, which are in essence the 'end-nodes' of a network path.
Servers can fail because of a hard drive failure, motherboard overheating, memory malfunction, operating system bug, web server software overload or any of a hundred other causes. Whatever the cause, when two or more servers are configured so that another can take up the slack from one that's failed, that is redundancy.
That is more difficult to achieve than network redundancy, but it is still very common. Not as common as it should be, since many times a failed server is just re-booted or replaced or repaired with another piece of hardware. But, more sophisticated web hosting companies will have such redundancy in place.
And that's one lesson for anyone considering which web hosting company may offer superior service over another (similarly priced) company. Look at which company can offer competent assistance when things fail, as they always do sooner or later.
One company may have a habit of simply re-booting. Others may have redundant disk arrays. Hardware containing multiple disk drives to which the server has access allows for one or more drives to fail without bringing the system down. The failed drive is replaced and no one but the administrator is even aware there was a problem.
Still other companies may have still more sophisticated systems in place. Failover servers that take up the load of a crashed computer, without the end-user seeing anything are possible. In fact, in better installations, they're the norm. When they're in place, the user has at most only to refresh his or her browser and, bingo, everything is fine.
The more a web site owner knows about redundancy and failover, the better he or she can understand why things go wrong, and what options are available when they do. That knowledge can lead to better choices for a better web site experience.
The History of Writing Tools (history of writing tools) Writing tools are essential to written communication. A person is not able to write without the proper writing tools. However, many people don’t realize that writing tools did not just pop into existence; writing tools have a long history. Writing tools have helped societies write their history and bring civilizations to life. The history of writing tools begins with the cave man that invented the sharpened-stone, which was later developed into the first writing tool. Cave men used these instruments to scratch pictures onto the walls of cave dwellings. The drawings were said to represent events in the daily life of the cave men, such as the planting of crops and hunting victories. Clay was later discovered, which made portable records possible, and many merchants of the time used clay token with pictographs to record the quantities of materials being traded and shipped. The Greeks developed the earliest form of pen and paper. They used the writing stylus, which could be made of metal, bone, or ivory, to make marks on wax-coated tablets. The tablets used by the Greeks were made in hinged pairs that were closed to protect the scribe’s notes. Cadmus was a Greek scholar who seemingly invented the written letter, which is a text message on paper sent from one individual to another. The written letter proved to be a major event in the history of writing tools, and was the starting point for the development of ink. “Indian Ink” was developed by the ancient Chinese society, and perfected for writing. The ink was originally designed for blacking the surfaces of raised stone-carved hieroglyphics, but was later used for writing. This early ink was made of a mixture of soot from pine smoke and lamp oil mixed with the gelatin of donkey skin and musk. By the year 1200 B.C. the ink had become common as a writing tool. Inks were also developed by other cultures, who used natural dyes and colors derived from berries, plants, and minerals to create them. The different colors of inks had ritual meanings attached to each color in early writings. In the history of writing tools the development of ink paralleled the introduction of paper. Early cultures such as the Egyptians, Romans, Greeks, and Hebrews used papyrus and parchment paper to write on. Romans invented a reed-pen for parchment and ink, from the hollow tubular-stems of marsh grass and the jointed bamboo plant. The bamboo stems were converted into writing tools that resemble the fountain pen. The plant was cut at one end into the form of a pen point, and ink filled the stem, by squeezing the reed, writers could force the ink from the point and write on parchment paper. The early forms of ink and paper were great developments in the history writing tools, but were often unstable. A stable form of ink was developed in 400 A.D., which was a composite of iron-salts, nutgalls, and gum. The ink was seen as having a bluish-black hue when applied to paper, but quickly becoming a darker black color, and fading after years and appearing as a dull brown color. The Chinese created a wood-fiber paper in 105 A.D., but it was not known to other cultures until 700 A.D. when the Japanese learned the secret. Eventually, the wood-fiber paper was brought to Spain in 711 A.D., but was not widely used in Europe, as most European societies did not use paper until the 14th century. The quill pen is also a major invention in the history of writing tools. The quill pen was introduced to the world in 700 A.D. The pen was made of bird feathers, and the strongest quills were typically taken from live birds from the outer left wing feathers. After the development of the quill pen, plant fiber paper became the popular medium for writing. Then another invention changed the history of writing tools; Johannes Gutenberg invented the printing press. This invention has led to various other developments in printing and writing tools. Writing tools are essential to writing, and without the development we would not be able to show others our ideas and thoughts. Web Hosting - Bandwidth and Server Load, What's That? Two key performance metrics will impact every web site owner sooner or later: bandwidth and server load. Bandwidth is the amount of network capacity available, and the term actually covers two different aspects. 'Bandwidth' can meanthe measure of network capacity for web traffic back and forth at a given time. Or, it sometimes is used to mean the amount that is allowed for some interval, such as one month. Both are important. As files are transferred, emails sent and received, and web pages accessed, network bandwidth is being used. If you want to send water through a pipe, you have to have a pipe. Those pipes can vary in size and the amount of water going through them at any time can also vary. Total monthly bandwidth is a cap that hosting companies place on sites in order to share fairly a limited resource. Companies monitor sites in order to keep one site from accidentally or deliberately consuming all the network capacity. Similar considerations apply to instantaneous bandwidth, though companies usually have such large network 'pipes' that it's much less common for heavy use by one user to be a problem. Server load is a more generic concept. It often refers, in more technical discussions, solely to CPU utilization. The CPU (central processing unit) is the component in a computer that processes instructions from programs, ordering memory to be used a certain way, moving files from one place to the next and more. Every function you perform consumes some CPU and its role is so central (hence the name) that it has come to be used as a synonym for the computer itself. People point to their case and say 'That is the CPU'. But, the computer actually has memory, disk drive(s) and several other features required in order to do its job. Server load refers, in more general circumstances, to the amount of use of each of those other components in total. Disk drives can be busy fetching files which they do in pieces, which are then assembled in memory and presented on the monitor, all controlled by instructions managed by the CPU. Memory capacity is limited. It's often the case that not all programs can use as much as they need at the same time. Special operating system routines control who gets how much, when and for how long, sharing the total 'pool' among competing processes. So, how 'loaded' the server is at any given time or over time is a matter of how heavily used any one, or all, of these components are. Why should you care? Because every web site owner will want to understand why a server becomes slow or unresponsive, and be able to optimize their use of it. When you share a server with other sites, which is extremely common, the traffic other sites receive creates load on the server that can affect your site. There's a limited amount you can do to influence that situation. But if you're aware of it, you can request the company move you to a less heavily loaded server. Or, if the other site (which you generally have no visibility to) is misbehaving, it's possible to get them moved or banned. But when you have a dedicated server, you have much more control over load issues. You can optimize your own site's HTML pages and programs, tune a database and carry out other activities that maximize throughput. Your users will see that as quicker page accesses and a more enjoyable user experience. |