Cloud computing
Cloud computing means using storage, processing power and software that are provided over the internet by remote servers, instead of owning and running them yourself. Email services, online document editors, photo backup and video streaming are all cloud services. The syllabus asks you to understand cloud computing, the difference between public and private clouds, and the benefits and drawbacks, usually in a scenario where an organisation is deciding whether to move to the cloud.
What cloud computing is
Cloud computing is the on-demand delivery of computing services (storage, processing, software and databases) over the internet from remote servers in data centres, typically paid for according to use.
The "cloud" is not mysterious: it is very large numbers of servers in data centres, owned by a cloud provider, connected to the internet. Users access them from any device with an internet connection and a browser or app. The provider is responsible for the hardware, power, cooling, physical security, maintenance and backups.
What can be provided
Cloud services are often described in three layers.
- Software as a service (SaaS): complete applications run in the cloud and used through a browser, such as webmail, online office suites and customer management systems.
- Platform as a service (PaaS): a platform on which developers build and run their own applications, with the operating system, database and web server already provided.
- Infrastructure as a service (IaaS): virtual servers, storage and networking, which the customer configures and manages as if they were their own machines.
Cloud storage (backing up or syncing files to a provider's servers) is the form most people use every day.
Public and private clouds
A public cloud is cloud computing provided by a third-party provider over the internet, with the same infrastructure shared by many different customers (each customer's data is kept separate). Anyone can pay to use it.
A private cloud is cloud computing infrastructure used by a single organisation only. It may be run on the organisation's own servers (in its own data centre) or hosted by a provider, but it is not shared with other customers, and is reached over the organisation's private network or a secure connection.
A hybrid cloud combines the two: for example, sensitive data is kept in a private cloud while the public cloud is used for less sensitive work or for extra capacity at busy times.
| Public cloud | Private cloud | |
|---|---|---|
| Who uses the infrastructure | Many customers, shared | One organisation only |
| Who owns and manages it | Third-party provider | The organisation (or a provider on its behalf) |
| Cost | No up-front hardware cost; pay for what you use | High set-up and running costs |
| Scalability | Almost unlimited, immediate | Limited by the hardware the organisation has bought |
| Control and security | Less control; data on third-party servers | Full control over data, security and location |
| Suits | Start-ups, individuals, variable demand | Banks, governments, hospitals with strict data rules |
Benefits of cloud computing
- No need to buy and maintain hardware. The provider supplies servers, storage and data centres, so there is no large up-front cost and no need for in-house technicians to maintain them.
- Pay for what you use. Costs scale with demand: a business pays for more capacity only when it needs it.
- Scalability. Storage and processing can be increased or reduced almost instantly, for example for a seasonal sales peak, without buying new equipment.
- Access from anywhere. Files and applications can be used from any device with an internet connection, which supports remote working and collaboration on the same documents in real time.
- Backup and disaster recovery. Providers keep copies of data in several data centres, so data survives a fire or hardware failure at the customer's premises.
- Automatic updates. Software in the cloud is updated by the provider, so users always have the latest version and security patches.
- Expertise. Large providers employ specialist security staff and run monitoring that a small organisation could not afford.
Drawbacks of cloud computing
- Internet dependence. Without a connection, or with a slow one, users cannot reach their data or applications. An outage at the provider stops everyone.
- Security and privacy. Data is stored on servers owned by a third party, possibly shared with other customers. A breach at the provider, or weak passwords on accounts, could expose it; the organisation has less control over who can access it.
- Legal issues. Data may be stored in other countries, where different data protection laws apply; some organisations are legally required to keep data in a particular country.
- Ongoing costs. Subscription fees continue for as long as the service is used and can rise; over many years they may exceed the cost of owning servers. Transferring large amounts of data may also cost money.
- Loss of control and lock-in. The organisation depends on the provider's reliability, pricing and continued existence; moving to another provider can be difficult.
- Performance. Transfer speeds over the internet are lower than on a local network, so working with very large files may be slow.
A new company of five people is developing a mobile app. It expects its number of users to grow quickly but unpredictably. Explain two reasons why it should use a public cloud.
Solution
- Low start-up cost: the company does not have to buy servers or build a data centre; it pays only for the resources it uses, which suits a small company with limited money.
- Scalability: if the number of app users grows suddenly, the company can increase its storage and processing capacity immediately in the public cloud, and reduce it again if demand falls. With its own servers it would have to predict demand and buy hardware in advance.
A hospital wants doctors to access patient records from any of its sites. Explain why it might choose a private cloud rather than a public cloud.
Solution
Patient records are highly confidential and subject to strict data protection laws. In a private cloud, the infrastructure is used only by the hospital, so it has full control over where the data is stored, who can access it and how it is secured; data is not on servers shared with other customers, possibly in another country. The hospital can still give doctors access from every site over its secure network. The trade-off is the higher cost of buying and running the infrastructure itself.
A school stores all students' work on its own file server. The head teacher proposes moving all files to a public cloud storage service. Discuss the benefits and drawbacks for the school.
Solution
Benefits:
- students and teachers can access files from home on any device, and collaborate on the same document;
- the school no longer needs to buy, maintain and replace its file server, saving technician time;
- the provider backs up data in several data centres, so work is not lost if the school's equipment fails;
- storage can be increased easily as the school grows.
Drawbacks:
- if the school's internet connection fails, nobody in school can open their files;
- many students accessing files at once needs a fast internet connection, which may cost more;
- students' personal data is held by a third party, possibly abroad, which raises privacy and legal concerns;
- subscription costs continue every year and may increase.
A reasoned conclusion: the school might adopt the cloud for anywhere-access and backup, but keep a fast connection and a contingency plan, and check that the provider meets data protection requirements.
An online shop keeps its customer payment data on its own servers but rents extra web servers from a public cloud provider during its annual sale. Name this arrangement and explain why it is used.
Solution
A hybrid cloud. Sensitive payment data stays on infrastructure the shop controls (private), for security and legal compliance. The public cloud provides extra capacity only when demand peaks, so the shop does not have to buy servers that would be idle for the rest of the year; it pays only for the days it uses them.
"The cloud means data is stored on the internet." Data is stored on physical servers in data centres owned by a provider; the internet is how you reach them.
"Private cloud means the data is private and public cloud means anyone can see it." In a public cloud each customer's data is still kept separate and protected. The difference is whether the infrastructure is shared between many customers or used by one organisation.
"Cloud storage is always secure because the provider handles it" / "always insecure". Both are too absolute. Providers have strong security, but data is held by a third party, and weak user passwords remain a risk.
Cloud questions are almost always "explain the benefits and drawbacks for [this organisation]". Pick the points that matter in the scenario: a small business cares about up-front cost and scalability; a hospital or bank cares about security, control and legal requirements; a remote workforce cares about anywhere-access and internet dependence. Each point should state the feature and its consequence.
When asked to compare public and private clouds, describe the same feature for both: "a public cloud's infrastructure is shared by many customers, whereas a private cloud is used by one organisation only".
- Cloud computing: storage, processing and software delivered over the internet from remote data centres, paid for by use.
- SaaS (applications), PaaS (development platforms), IaaS (virtual servers and storage).
- Public cloud: provider's shared infrastructure, cheap to start, highly scalable, less control.
- Private cloud: one organisation only, more control and security, more expensive.
- Hybrid cloud: a mix of both.
- Benefits: no hardware to buy or maintain, pay per use, scalable, access anywhere, provider backups and updates.
- Drawbacks: needs an internet connection, third-party security and privacy concerns, legal issues of data location, ongoing costs, provider dependence.
Practice
- Define cloud computing.
- Explain the difference between a public cloud and a private cloud.
- Give two benefits of using cloud storage for an individual's photographs.
- Give two drawbacks of a company storing all its data in a public cloud.
- Explain why a company with highly variable demand might use cloud computing rather than its own servers.
- A government department is required by law to keep citizens' data within its own country. Explain how this affects its choice of cloud computing.
- A user's laptop is stolen. Explain how cloud storage could reduce the impact on the user, and one new risk that cloud storage introduces.
- Explain what is meant by software as a service, and give one advantage to a business.
- A film editing company works with very large video files. Evaluate the use of a public cloud for storing and editing these files.
- A secondary school with 1500 students currently runs its own servers. Write a recommendation, with reasons, on whether the school should use a public, private or hybrid cloud, considering cost, security and access.
Answers
- The delivery of computing services such as storage, processing and software over the internet from remote servers in data centres, usually paid for according to use.
- A public cloud is run by a third-party provider and its infrastructure is shared by many customers; a private cloud's infrastructure is used by one organisation only, which has full control over it.
- The photographs are backed up off-site, so they are safe if the device is lost or damaged; they can be accessed from any device with an internet connection; storage can be increased easily.
- Needs a reliable internet connection to access the data; data is held by a third party, so there are security, privacy and legal (data location) concerns; ongoing subscription costs; dependence on the provider.
- Cloud resources can be scaled up when demand is high and down when it is low, and the company pays only for what it uses. With its own servers it would have to buy enough hardware for peak demand, which would be idle most of the time.
- A public cloud provider might store the data in data centres in other countries, breaking the law. The department should use a private cloud (or a provider that guarantees storage within the country), so it controls where the data is stored.
- Files saved to the cloud are not lost with the laptop and can be accessed from a new device immediately; the thief cannot get them from the laptop if it is protected and they are not stored locally. New risk: if the account password is weak or reused, anyone who obtains it can access all the files from anywhere.
- Applications are run on the provider's servers and used through a browser or thin app, usually on subscription. Advantage: no installation or update of software on each computer, and costs are spread over time.
- Benefits: no need to buy large local storage; files can be shared between editors in different places; storage scales with demand and is backed up. Drawbacks: very large files take a long time to upload and download, needing a very fast connection; editing over the internet may be slow; ongoing costs for large amounts of storage and data transfer may be high; unreleased films are commercially sensitive. A sensible conclusion: keep working files on fast local storage and use the cloud for backup and sharing finished material.
- A good answer weighs the options. For example: a hybrid cloud. Use a public cloud SaaS service for documents and email, giving anywhere-access, collaboration and provider backups without buying servers; keep the most sensitive data (safeguarding records, exam data) in a private cloud or on servers the school controls, to meet data protection requirements. Ensure a fast, reliable internet connection and strong authentication.