About a year ago, General Manager of Unicom wrote an article "Cloud Computing I Know", which explained the various new technologies and concepts of cloud computing in a simple and simple way. In the past year, the development of cloud computing has been surging, and there have been many changes. After a period of comprehensive study and thinking, I also wrote a piece of my own understanding. Many of these viewpoints are extremely extreme, and they are a good example. The core to be said is: there is no cloud in the world, there are more people talking, Yunshan is foggy, and people are clouded, so cloud computing becomes a trend. Everyone is used to using software and hardware to distinguish the components of the computer. In general terms, hardware is the physical platform provided for computer systems, and software is on the hardware platform, presenting a variety of functions. Both have a division of labor and coordinated development, which constitutes a complicated computer world. I still remember that the university developed on 51 single-chip microcomputers. Compared with BASIC and FORTRAN, C language was the most advanced programming language at that time. Technical experts use assembly language for development. Although it is difficult to master, the object of operation is register or memory, so the execution speed is extremely fast. At that time, hardware resources were scarce and expensive. If you can save a few lines of code and consume less resources, you can directly reflect the huge value. The subsequent development is mainly driven by hardware vendors, but the development model is precisely to improve the competitiveness of hardware by developing software. On the one hand, the development of the operating system, while reducing the threshold of software development, makes the system software and hardware tightly bundled together; on the other hand, hardware vendors also use the dominant position of the platform to create hardware suitable for different types of applications. platform. For example, the mainframe and fault-tolerant machines widely used in the banking industry provide a stable and reliable computing platform. Although expensive and redundant, the stability and reliability are perfect. For example, NCR's data warehouse solution is also soft. The hardware is integrated and performs well in data analysis. Various computer hardware have relative application scenarios, especially in the middle and late last century, various hardware platforms have been continuously improved, the volume is getting smaller and smaller, the capacity is getting bigger and bigger, the integration is getting higher and higher, and the performance is getting stronger. . Of course, because the UNIX minicomputer has the best overall performance in terms of openness, stability, and cost, it is the hardware platform for the most widely used computer systems. PC servers, although low in cost, are difficult to enter the enterprise and large-scale computing fields due to shortcomings such as poor stability, high failure rate, and low performance. In this process, the driving force of development mainly comes from two aspects: First, Moore's Law, the rapid advancement of integrated circuits, promoted the development of hardware platforms, all kinds of servers are constantly innovating, and new products with better performance and lower prices will be launched almost every year; Second, the wave of IT system initial construction, all units are developing IT, using computer systems to replace manual work, from the endless to build IT systems, can be described as a hundred flowers. Due to the differences in various applications, stability, security, business continuity and other requirements are different, so all kinds of hardware have very good market space. Having said that, I also thought of an episode: In the early years, some people said that the overseas IT system represented by the United States is based on hardware and software that has remained unchanged for decades. The performance is also very stable; The most advanced hardware equipment, is this not a waste of money? In my understanding, the two are only different stages of IT development: domestic IT companies are developing rapidly, especially the user scale and system complexity far exceed those of overseas operators, so it is not wrong to use the latest and best servers. The initial stage of IT in overseas is much earlier than in China. If the system capacity is satisfied, the demand changes little, and the cost of change is high, there is no need to update the equipment frequently. Therefore, when the Internet of the United States re-emerges, it puts new demands on IT and provides a soil for the growth of a series of new technologies such as cloud computing. The Internet has grown up on the basis of communication and computer networks, and the development of the Internet has brought opportunities and challenges to the communications and computer fields. A typical example is that compared to traditional computer systems, the Internet requires a larger amount of computing power, while also hoping to reduce costs as much as possible, so X86 servers are popular. What is the performance of a single machine? Rely on the software heap. Hardware is unstable, what should I do? Rely on software. What do you need to change quickly? Rely on software. Many technologies in the field of cloud computing have been forced out. Internet start-ups are masters of saving money, and they can't wait for a penny to be split into two halves. Therefore, they love the IT platform with the lowest cost performance. The beneficiary of the last round is SUN. Nowadays, X86 server has gradually become the standard of a new generation of Internet companies. When a company does not have so many money to buy a machine, it uses the Internet sharing mode to rent computing power and storage resources according to actual needs. This is the source of power for cloud computing. . At the same time, "saving money" has contributed to the prosperity of open source technology. From a technical point of view, open source code, through community communication and gradual improvement, these are very consistent with the Internet development ideas; but from a business perspective, free open source software seriously affects the economic benefits of traditional IT companies, but also inhibits traditional IT The innovation power of enterprises has made the traditional IT industry worse. Among the many hardware genres, X86 has unparalleled cost advantages, and naturally becomes the key development area of ​​cloud computing technology. The driving force of the rapid development of the Internet is mainly for the X86 platform; while other hardware is large in scale and high in cost. There is limited room for change, and not many Internet companies are willing to innovate on this. In a few years, the mainframe relied on the advantages of security and stability to adhere to the traditional site, and some of the minicomputers and software were deeply integrated into one machine, and more hardware manufacturers gave up their own development plans. Future IT systems, especially new systems, can only grow on the basis of a piece of X86 server. For most application scenarios, in addition to X86 in the future, there may be no other hardware platforms available. Based on the same X86 server, the different gameplay methods have spawned different cloud computing technologies. The most familiar and accepted is the virtualization technology. The so-called virtualization is mainly to divide large and complete hardware resources (including calculation, storage, etc.) into smaller units, and has the ability to dynamically adjust small units. If virtualization is used well, it can be flexibly allocated and timely. Scheduling and calculating storage resources to improve resource utilization efficiency. It is worth mentioning that virtualization technology is not unique to X86. In fact, deploying virtualization software on a minicomputer is a model that IT systems often use today. This is because a single minicomputer has more resources than the X86, so deploying virtualization on a minicomputer is often better than deploying on the X86 in terms of resource utilization, and even has a cost advantage over the X86. For example, the current system of operators is based on minicomputers, and many small applications run on the virtualization software of minicomputers. However, with the X86 as the main system in the future, there is no need to deploy virtualization software on the minicomputer, and more virtualization scenarios will be transferred to the X86. Therefore, the virtual machine scene of the minicomputer will be less and less, and the remaining minicomputers will mainly meet the large computing needs. That is to say, the traditional minicomputer is gradually shrinking and withdrawing, which is only a matter of time. Virtualization technology is to make large resources small, then, how to combine small resources into a platform for large-scale computing? This requires another type of cloud computing technology: distributed computing. Why is this a type of technology? Although the needs of different families are different, the application scenarios are different, and the technologies and strategies adopted are quite different. The conventional grid computing, clustering, and the special technologies of many Internet companies seem to be varied, and in fact, they are inseparable from each other. It is how to combine small computing resources into a large-scale computing platform. Although the current virtualization + X86 model is the most widely used, not all cloud computing is based on virtualization technology. The most typical of these is Google. As an Internet company that provides search services, Google needs to solve the problem of not using virtualization technology. On the contrary, deploying virtualization software will reduce system operation efficiency and increase costs. Therefore, Google develops its own products based on its own needs. First, it makes Map/Reduce and NDFS for enterprise use. On this basis, it forms a classic Hadoop platform, from "self-research" to "self-use" to "product." "," admirable. On this basis, Google continued to innovate, and even led to the "container" technology revolution and Kubernetes's arrogant rush, which is a post-mortem, for the time being. As mentioned earlier, due to the impact of the Internet, the decline of traditional hardware platforms is not appropriate. But systems that use low-cost X86 and free open source software need to do more work in terms of security, stability, resource scheduling and management, and system development complexity. Supported management to solve. As a result, many new technologies came into being.
Absolute rotary Encoder measure actual position by generating unique digital codes or bits (instead of pulses) that represent the encoder`s actual position. Single turn absolute encoders output codes that are repeated every full revolution and do not output data to indicate how many revolutions have been made. Multi-turn absolute encoders output a unique code for each shaft position through every rotation, up to 4096 revolutions. Unlike incremental encoders, absolute encoders will retain correct position even if power fails without homing at startup.
Absolute Encoder,Through Hollow Encoder,Absolute Encoder 13 Bit,14 Bit Optical Rotary Encoder Jilin Lander Intelligent Technology Co., Ltd , https://www.jilinlandertech.com