Applying Virtualization and System Usage/Operation Modes
標準~39 min7 terms7 past questions
Goals of this unit
Explain thin clients (シンクライアント) and VDI separately: one is a way of structuring a system, the other is the infrastructure that supports it.
Tell migration (マイグレーション) from live migration (ライブマイグレーション) by whether processing stops during the move.
Separate batch processing (バッチ処理) from other processing modes by whether data is handled right away or stored first, and tell interactive processing (対話型処理) from real-time processing (リアルタイム処理) by what each puts first: exchanges with a person, or a response deadline.
A thin client (シンクライアント) is a system setup in which the terminal keeps only minimal functions such as input and screen display, while running applications and storing data are concentrated on the server side.
What the user does on the terminal is sent to the server, and the screen showing the server's result comes back to the terminal. Because business data is not saved on the terminal's storage, a lost or stolen terminal is less likely to leak information, and software updates can be applied on the server side in one place. On the other hand, if the network or the server goes down, the terminal alone cannot keep the work going.
AnalogyIt is like a reading seat in a library. The seat has only a desk and a lamp, the books stay in the stacks, and staff show just the page you want on the seat's screen. Even if you carried the seat home, no book would come with it.
How to rememberThin refers to how little the terminal does, not to its physical shape, and its opposite is fat. The ordinary PC style, where the terminal holds both processing and data, is called a fat client (ファットクライアント).
Exam points
ExamBusiness data is not saved on the terminal's storage, so losing the terminal rarely leaks information. Because of this, thin clients are adopted as a measure against information leakage (情報漏えい対策).
ExamThe server runs the applications and manages files and other resources, while the terminal handles only input and output with the user.
VDI (Virtual Desktop Infrastructure) runs each user's desktop environment in a virtual machine on a server, and the user operates that screen remotely from a terminal.
Input on the terminal
Send the input to the server
The user's virtual machine processes it
Return only the screen to the terminal
Only the resulting screen returns to the terminal, and the data stays on the server.
4 / 4
A virtual machine is a virtual computer built by software inside one physical server, and VDI assigns one to each user. The terminal sends input and receives only screen information, so VDI is used as a way to achieve a thin client, where the terminal holds neither processing nor data. OS updates and security measures can also be handled together on the server.
AnalogyIt is like keeping your own private study at a hotel front desk. Whichever branch you stay at, once you get the key you can enter the same study.
How to rememberIt stands for Virtual Desktop Infrastructure. The name shows that what is virtualized is not a server but the desktop, meaning the user's screen environment.
Thin Client vs. VDI
Aspect
Thin Client
VDI
Key differenceRefers to
The idea of a setup that keeps processing and data off the terminal
Infrastructure that runs desktop environments in virtual machines on a server
Migration (マイグレーション) means moving a system, data, a virtual machine, or similar from its current environment to another one.
Switching from an old server to a new one, or moving in-house servers to the cloud, are examples. In virtualization, moving a virtual machine to another physical server is also called migration. The word does not limit how the move is done and broadly covers the act of moving itself.
AnalogyIt is like moving house. You carry your belongings from the current home to the new one so you can go on living the same way there.
How to rememberTo migrate is for people or animals to move where they live, as birds do each season. The image behind the word is changing one's home.
Live migration (ライブマイグレーション) moves a running virtual machine to another physical server without stopping it, so it keeps processing at the destination.
Running on the source
Transfer memory contents and more
Switch processing to the destination
Keep running on the destination
The virtual machine carries on at the destination from where it left off before the switch.
4 / 4
Even during physical server maintenance or hardware replacement, service to users does not have to stop. It can also shift virtual machines from a heavily loaded physical server to one with spare capacity to share the load.
AnalogyIt is like moving passengers from a moving train onto another train running alongside it. The passengers keep heading to their destination without breaking their journey.
How to rememberLive as in a live broadcast. Picture switching studios without interrupting the broadcast: not stopping is built into the name.
Exam points
ExamIn live migration (ライブマイグレーション), the destination physical server takes over processing from the state just before the move, so there is no need to stop the virtual machine and start it again from the beginning.
Interactive processing (対話型処理) is a processing mode in which the computer responds each time the user acts, and work moves forward through these repeated exchanges.
For example, typing in a word processor changes the screen at once, and entering a search term shows a list of results. The user looks at what comes back and decides the next action, so human judgment is built into the flow of processing.
AnalogyIt is like asking someone for directions. You ask, you get an answer, and you base your next question on that answer.
How to rememberIn English it is interactive: inter (between each other) plus act, describing a person and a machine taking turns.
Exam points
Mix-upInteractive processing (対話型処理) moves forward by responding to each action, while batch processing (バッチ処理) processes data stored up to a cut-off all together later.
Real-time processing (リアルタイム処理) is a processing mode that handles a request or data as soon as it arises and returns the result within a set time.
It is used where a late result causes trouble, such as train seat reservations or controlling factory machines. What it requires is less raw speed than the ability to respond by the set deadline.
AnalogyIt is like a fire station taking an emergency call. It acts the moment the call comes in and is expected to meet its target arrival time.
How to rememberReal time means time in the real world: processing keeps pace with events as they actually happen.
Exam points
ExamA system that handles processing requests sent from terminals over a network on the spot and returns the results at once is called an online real-time system (オンラインリアルタイムシステム).
Mix-upInteractive processing (対話型処理) centers on exchanges with a person, while real-time processing (リアルタイム処理) centers on a response deadline. Even machine control with no human operator counts as real-time processing if it needs a response within the deadline.
Batch processing (バッチ処理) is a processing mode that stores data until a set period or count is reached and then processes it all at once.
Store data as it arises
Reach the set cut-off
Process the stored data at once
Output the results together
The results are output together as reports or files.
4 / 4
It suits processing that does not need a response for each item and clears large volumes of data efficiently. Totaling a month of sales slips on the closing date, or running work together at night when usage is low, are examples. One unit of work that a computer is given to run as a whole is called a job (ジョブ), and batch processing runs several jobs in a set order.
AnalogyIt is like piling laundry in a basket and running the washing machine once when the basket is full.
How to rememberA batch originally meant one oven load of bread. Link it to gathering everything for one baking before it goes into the oven.
Exam points
ExamBatch processing is a method that processes, in one go, data collected until a period or count cut-off.
ExamWhen the CPU and the output device can work independently, the next job's (ジョブ) CPU processing can proceed while the previous job is being output. Each job's output starts at whichever comes later: the end of its own CPU processing or the moment the output device becomes free.
A thin client (シンクライアント) limits the terminal to input and output and keeps processing and data on the server, which curbs information leaks from terminals.
VDI is infrastructure that runs desktop environments in virtual machines on a server.
Live migration (ライブマイグレーション) moves a virtual machine to another physical server while it keeps running, allowing maintenance or load balancing without stopping service.
Batch processing (バッチ処理) handles data stored up to a cut-off in one go, so it clears large but non-urgent workloads efficiently.