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* Description: Knowledge of server CPU, memory, disk hardware structure
* Date: 03:38 PM EST, 06/25/2017
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<1> Server hardware structure:
     |
     |__ o. For majority of current laptop, computer or server, there are 3 essential components within it. Ihey are CPU, memory, and disk.
     |      You may also hear several terminologies associated with them, such as system process, memory allocation, and disk Input/Oput.
     |      So, how are they related to each other? And why the computer is being designed in this way?
     |		
     |__ o. Let us image a senorio that a student sitting in a classroom, and doing a mathmatic exam.
		 
             >> He is reading the question from the exam paper, and holding a draft paper on his desk.
             >> There is one question asking if x=3, what is the result of this function f(x)=x3+x2+x.
             
             >> Now, his brain is analogy to Cpu of a computer.
             >> Exam paper is a hard disk. The question on the exam paper is like a piece of “computer program” lying on the disk statistically.
             >> The draft paper is memory.
             
             >> First, the brain start reading the question by his eyes. This reading action is called “disk output”.
             >> After getting the question, the brain will move to draft paper to find a blank area for testing caculation. This action is called "memory allocation".
             >> When the result comes up, the brain will ask his hand to write the result back to the exam paper. This action is called "disk input".
             >> The combination of his eyes and hands, we call it as "I/O device" of a server.
             
             >> When his brain is thinking the question is like the program is running in the CPU. 
                The running program with real data, we call it as a "process". In this case, the real data is x=3.
				

				
<2> Disk I/O speed:
     |
     |__ o. Attention: the speed of CPU accessing memory is extremely faster then I/O device reads or writes data into a disk.
     |
     |       >> We usually measure CPU speed in nanosecond, but measure disk speed in millionsecond.
     |       >> If CPU is a like jet fast, then disk is a snail.
     |        
     |__ o. Let us review the inside structure of a HHD drive to find why.
             
             >> This is storage media. All the data are being saved here.
             >> Everytime, CPU sends over an I/O request, and disk arm has to take some time to search where the data block is on the disk, and perform read/write action. 
             >> So, the machinical searching and movement will take some time. 
             >> In contrast, the CPU access memory electronically, which would be much faster.