Cloud computing is the use of internet-based servers, storage, databases, networking, and software instead of only using a local computer or school server. This cheat sheet helps students understand how cloud systems support websites, apps, file storage, gaming, streaming, and artificial intelligence tools. It is useful because many modern computer science projects depend on cloud platforms for speed, reliability, and flexible resources.
The core ideas include service models such as IaaS, PaaS, and SaaS, plus deployment models such as public, private, hybrid, and community clouds. Students should understand virtualization, scalability, availability, latency, and the shared responsibility model. A strong cloud design balances performance, cost, security, and reliability.
Key Facts
- Cloud computing means using remote servers over the internet to store, process, and manage data instead of relying only on local hardware.
- IaaS means Infrastructure as a Service, where the provider supplies virtual machines, storage, and networks while the user manages operating systems and apps.
- PaaS means Platform as a Service, where the provider manages the infrastructure and development platform so users can build and deploy applications.
- SaaS means Software as a Service, where users access complete applications through a browser or app, such as email, document editors, or file storage.
- Scalability means a system can increase or decrease resources, such as CPU, memory, or storage, to match demand.
- Availability is often written as uptime percentage, and availability = working time / total time x 100%.
- Latency is the delay between a request and a response, so lower latency usually means a faster user experience.
- The shared responsibility model means the cloud provider secures the cloud infrastructure while the customer secures their data, accounts, settings, and applications.
Vocabulary
- Cloud Computing
- Cloud computing is the delivery of computing resources such as servers, storage, databases, and software over the internet.
- Virtualization
- Virtualization is the process of creating software-based versions of hardware resources, such as virtual machines running on physical servers.
- IaaS
- IaaS is a cloud service model that provides basic computing infrastructure like virtual machines, storage, and networking.
- PaaS
- PaaS is a cloud service model that provides a managed platform for building, testing, and deploying applications.
- SaaS
- SaaS is a cloud service model that provides ready-to-use software delivered through the internet.
- Scalability
- Scalability is the ability of a system to handle more or fewer users or workloads by adjusting its resources.
Common Mistakes to Avoid
- Confusing cloud storage with the whole cloud is wrong because cloud computing also includes processing power, databases, networking, security, and application services.
- Thinking the cloud is not physical is wrong because cloud services still run on real servers in data centers connected by networks.
- Mixing up IaaS, PaaS, and SaaS is wrong because each model gives the customer a different level of control and responsibility.
- Ignoring security settings is wrong because customers are still responsible for passwords, permissions, data protection, and application security in most cloud services.
- Assuming cloud services are always cheaper is wrong because poor resource management, unused servers, high data transfer, and over-scaling can increase costs.
Practice Questions
- 1 A website had 716 hours of working time during a 720-hour month. Calculate its availability percentage using availability = working time / total time x 100%.
- 2 A cloud server costs $0.12 per hour. How much does it cost to run continuously for 30 days?
- 3 Classify each service as IaaS, PaaS, or SaaS: a virtual machine, an online email app, and a managed app development platform.
- 4 A school wants to move student files and a learning website to the cloud. Explain two benefits and two risks the school should consider before migrating.
Understanding Cloud Computing Basics
Virtualization makes it possible for one powerful physical machine to behave like many separate computers. A program called a hypervisor divides processor time, memory, storage, and network access among virtual machines. Each virtual machine can run its own operating system.
This improves hardware use because a server rarely needs to sit idle for one task. Containers are another common tool. They package an application with the files it needs, but they share the host operating system.
Containers usually start faster than virtual machines. Students should notice that isolation is useful, but it is not perfect. A weak configuration can still expose data or allow one workload to affect another.
A busy online service must handle changing demand. A load balancer sends incoming requests across several running copies of an application instead of sending everything to one machine. If traffic rises, automatic scaling can start more copies.
If traffic falls, it can remove copies to reduce waste. This works best when the application stores important user data in a separate database or storage system. Otherwise, a user may reach a different copy and lose their session or progress.
Caching can make repeated requests faster by keeping commonly used data nearby. Caches must be updated carefully, since old cached data can give users the wrong result.
Location affects how a cloud system behaves. Data centers are grouped into regions, which are broad geographic areas. A region may contain several separate zones with independent power, networking, and buildings.
Running copies in more than one zone helps a service continue after a hardware failure or local outage. Copies of data are often replicated across machines or locations. Replication improves recovery, but it creates a tradeoff.
A system may show a slightly older version of data for a short time while updates travel between locations. Backups matter even when replication exists. Replication can copy a mistake, such as an accidental deletion, while a backup preserves an earlier version.
Security depends heavily on choices made by the people using a platform. An account with broad permissions can cause major damage if its password is stolen. Strong systems use separate accounts for separate jobs, limited permissions, multi factor sign in, and careful handling of secret keys.
Encryption protects data while it moves across networks and while it is stored, but encryption does not fix a public file folder or a careless access rule. Logging records important events, such as sign ins, failed requests, and changes to settings.
Monitoring turns those records into useful warnings. When learning cloud computing, pay attention to diagrams that show where data travels, who can access it, what happens during failure, and which resource creates the largest cost.