Your photos, your school email and your games saves may all live in the cloud: on servers you will never see, reached over the internet. Learn what cloud computing really is, the difference between public and private clouds, and how to weigh the benefits against the risks.
Cloud computing is the delivery of computing services (storage, processing power, software and platforms) on demand, over the internet, from remote servers in data centres. A public cloud is run by a provider and its servers are shared by many organisations and members of the public, who pay for what they use. A private cloud is used by a single organisation, either on its own premises or hosted for it, giving more control and security. Benefits include access from anywhere, scalability and no hardware to maintain; drawbacks include dependence on the internet connection, security and privacy concerns and loss of control over the data.
Fig. 1: a public cloud is shared by many users; a private cloud serves one organisation
Section 01
What is the cloud?
"The cloud" is not in the sky. It is racks of servers in data centres, owned by a provider and reached over the internet.
Storage: files are saved on remote servers, e.g. online file storage and photo libraries, and synchronised across a user's devices.
Software (applications): programs run on the provider's servers and are used through a browser, e.g. online office suites and webmail. Nothing needs installing.
Platform and infrastructure: organisations rent processing power, servers, databases and development platforms instead of buying their own hardware.
Pay as you go: users rent the service and pay for what they use; capacity can be increased or reduced on demand.
Examiner trap
Cloud storage is not the same as a local file server. The data is held off-site by a third party and reached over the internet, which is exactly why the benefits and drawbacks differ.
Section 02
Public or private?
Both are clouds: the difference is who shares the hardware and who controls it.
Public cloud
Private cloud
Who uses it
many organisations and individuals share the provider's servers
one organisation only
Who runs it
a third-party provider
the organisation itself, or a provider hosting it for that organisation alone
Cost
low start-up cost; pay per use
expensive: hardware, buildings and staff, or a dedicated hosting contract
Control and security
less control; data stored alongside other customers'; provider handles security
full control over where data is held, who can access it and how it is secured
Scalability
almost unlimited, on demand
limited by the hardware the organisation has
Suits
a start-up, a school, individual users
a bank, a government department, a hospital with sensitive data
A hybrid cloud combines both: sensitive data in a private cloud, other services in a public cloud.
Stage 1 · Learn
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What is cloud computing?
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What makes a cloud private?
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Which is a drawback of using a public cloud?
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What does scalable mean for a cloud service?
Section 03
Benefits and drawbacks.
This is where marks are won or lost: each point must be explained in context, not just listed.
Benefits
Drawbacks
data and software can be accessed from any device, anywhere with an internet connection
no internet connection (or a slow one) means no access to the data or software
no need to buy, house or maintain servers; the provider carries out maintenance and updates
ongoing subscription costs can exceed the cost of owning the hardware over time
scalable: storage and processing can be increased instantly when needed
data is held by a third party: risk of hacking, and concerns about privacy and who can see it
the provider makes backups, often in several locations, so data is protected against local disasters
loss of control: the provider may change prices or terms, suffer an outage or go out of business
easy collaboration: several users can work on the same file at the same time
data may be stored in another country, under different data protection laws
Worked example Weigh it up
A small architecture firm of 8 staff is deciding whether to store its drawings in a public cloud. Give one benefit and one drawback, each in context.
Benefit: staff can open the drawings on site visits from any device with an internet connection.
The firm does not need to buy a file server or employ a technician, because the provider maintains the hardware and backups.
Drawback: if the office internet connection fails, staff cannot open the drawings they need.
The drawings are confidential client work held by a third party, so there is a risk of unauthorised access.
Answer: Access from anywhere with no hardware to maintain, against dependence on the internet and the security of a third party
Your turn
Why might a hospital choose a private cloud rather than a public cloud for patient records?
Patient records are highly sensitive personal data. A private cloud is used by the hospital alone, so it keeps control over where the data is stored, who can access it and how it is secured.
Examiner trap
"Cloud is cheaper" is only true for start-up costs. Over many years the subscription can cost more than owning the hardware, so qualify the claim.
Stage 2 · Exam
Exam-style questions
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A government department must keep tight control over where its secret data is stored. Which is most suitable?
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Which is a benefit of cloud computing for a new company?
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Why may storing personal data in a public cloud raise legal concerns?
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Which describes a hybrid cloud?
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