Public cloud (パブリッククラウド) is a model in which facilities prepared by a cloud provider are shared over the internet by many unspecified users.
Users do not buy their own equipment; once they sign up they can start within a short time, and they pay for what they use. Because many users split the facilities, the cost per company tends to stay low and it is easy to scale with rising or falling demand. On the other hand, settings and features must be chosen from what the provider offers.
AnalogyA laundromat, where many people take turns using the shop's machines. You do not buy a washer yourself; you pay only for each load.
How to remember"Public" means open to everyone. Picture a public phone booth that anyone can use.
Exam points
Mix-upUsers of a public cloud (パブリッククラウド) share the provider's facilities with other users. Having an environment dedicated to your own company belongs to the private cloud (プライベートクラウド) side.
Private cloud (プライベートクラウド) is a model in which a single, specific organization uses cloud technology exclusively.
It may be built in the company's own data center, or set up by renting part of a provider's facilities as a dedicated section. Since the facilities are not shared with other organizations, it is easier to configure them around the company's own security measures and business needs. In return, the effort and cost of building and managing it tend to fall on the company.
AnalogyA staff cafeteria only employees can enter. You do not share seats with outsiders and the company can set the menu, but the company also pays to run it.
How to remember"Private" means belonging to particular people. Think of a private beach that only certain people may use.
Exam points
Mix-upA private cloud (プライベートクラウド) is not defined by where it is located. Even inside a provider's facility, it is a private cloud as long as one organization uses it exclusively.
Hybrid cloud (ハイブリッドクラウド) is a model that links environments of different kinds, such as a public cloud and a private cloud (or in-house equipment), and uses each for the purposes it suits.
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For example, customer information that must not leave the company is kept in the dedicated environment, while a sales site whose traffic swings sharply with the seasons runs in the shared one. The aim is to get both confidentiality and easy scaling. However, the mechanisms and management for moving data between the environments tend to become complicated.
AnalogyChoosing between a meeting room only your staff can enter and a lounge shared by every tenant in the building, depending on the topic. Confidential talks go to the private room; casual catch-ups happen in the lounge.
How to rememberA hybrid car combines two different power sources, an engine and a motor. Mixing things of different kinds is the clue behind "hybrid."
Multi-cloud (マルチクラウド) is a model that uses services from several cloud providers side by side.
Providers differ in their strengths and pricing, so you can pick the service that fits each use and combine them. Besides reducing the risk that one provider's outage stops everything, it helps avoid a state where switching away from a particular provider becomes hard (vendor lock-in). On the other hand, operations take more work because each provider has its own controls and contracts.
AnalogyHaving your salary paid into Bank A while using Bank B for online payments, one account per purpose. If one bank has trouble, not everything stops.
How to remember"Multi" means many. Just as a multilingual person switches between languages, picture dealing with several providers at once.
Exam points
Mix-upMulti-cloud (マルチクラウド) focuses on the number of providers, while hybrid cloud (ハイブリッドクラウド) focuses on linking environments of different kinds. Some setups fit both.
Hybrid cloud vs. Multi-cloud
Aspect
Hybrid cloud
Multi-cloud
Key differenceWhat is combined
Environments of different kinds (shared and dedicated, etc.)
Services from several providers
Main aim
Both confidentiality and easy scaling
Choosing providers that suit each use and spreading dependence
What gets harder
Linking the environments
Managing each provider's different controls and contracts
On-premises (オンプレミス) is a model in which information system equipment is installed at a site the company manages and run by the company itself.
On-premises
Public cloud
Who prepares and manages the facilities
The company itself
The cloud provider
How costs arise
Equipment purchase cost comes first
Pay for what you use
Before you can start
Equipment must be procured and installed
Usable shortly after signing up
It is the approach used since before the cloud spread, and it serves as the baseline when comparing cloud models. Because the company prepares and manages the equipment, it can decide the configuration and security measures on its own. In exchange, the company has to provide the purchase cost, the installation space and the staff for maintenance.
AnalogyLiving in a home you own instead of renting. You can change the layout freely, but the purchase price and repairs are all on you.
How to remember"Premises" means a building and its grounds, so on-premises reads as "on the company's own grounds."
Exam points
ExamOn-premises (オンプレミス) is the name for a model in which equipment is placed at a site under the company's control and the company handles everything up to operation.
Mix-upEven an environment at the company's own site and run by the company can also be called a private cloud (プライベートクラウド) when it uses cloud technology for one organization's exclusive use.
A managed service (マネージドサービス) is a service in which a specialist provider takes over the operation and maintenance of a system.
The tasks handed over include, for example, monitoring operations, responding to failures and updating software. Users need not keep dedicated operations staff in-house and can focus more easily on their core business. The scope and cost are set by contract, so you need to confirm in advance where the provider's responsibilities end.
AnalogyLeaving an apartment building's cleaning and equipment checks to a management company. Residents do not handle daily upkeep, but the management contract decides what is covered.
How to remember"Managed" means looked after. Read it as "someone else manages it for you."
Exam points
Mix-upA managed service (マネージドサービス) focuses on who handles operation and maintenance, a different dividing line from the one that separates public cloud (パブリッククラウド) and private cloud (who you share facilities with).
Key points
With on-premises, the company bears the equipment cost and maintenance staff, but in return it decides the configuration and security measures itself.
A deployment model is not fixed once for the whole organization; it can be chosen per system or per use.
When choosing a model, compare factors such as cost, confidentiality, how fast you can start, and how much you would depend on a particular provider.