Unit
- On-demand self-service: A consumer can provision computing capabilities, such as server time and network storage, as needed automatically without requiring human interaction with each service provider. This eliminates delays in resource procurement.
- Broad network access: Capabilities are available over the network and accessed through standard mechanisms that promote use by heterogeneous thin or thick client platforms, including mobile phones, tablets, laptops, and workstations.
- Resource pooling: The provider's computing resources are pooled to serve multiple consumers using a multi-tenant model, with different physical and virtual resources dynamically assigned and reassigned according to consumer demand. There is a sense of location independence.
- Rapid elasticity: Capabilities can be elastically provisioned and released, in some cases automatically, to scale rapidly outward and inward commensurate with demand. To the consumer, the capabilities available for provisioning often appear to be unlimited.
- Measured service: Cloud systems automatically control and optimize resource use by leveraging a metering capability at some level of abstraction appropriate to the type of service. Resource usage can be monitored, controlled, and reported, providing transparency for both the provider and consumer.
- Business drivers for cloud adoption: Organizations move to cloud to achieve cost efficiency (pay-as-you-go), scalability to handle variable workloads, and global reach without building physical data centers.
- Cloud vs. traditional IT: Traditional IT requires upfront capital expenditure, long procurement cycles, and capacity planning. Cloud replaces capital expense with operational expense and offers agility.
- Common misconceptions: Cloud is not always cheaper; costs depend on usage patterns and data egress. Security is a shared responsibility between provider and customer.
- Service models (IaaS, PaaS, SaaS): Cloud services are generally categorized into three primary models. Infrastructure as a Service (IaaS) delivers fundamental compute, network, and storage resources. Platform as a Service (PaaS) provides a managed platform for developing and deploying applications. Software as a Service (SaaS) delivers ready-to-use software applications over the internet. Each model abstracts a different layer of the technology stack, shifting management responsibilities from the consumer to the provider.
- Deployment models: The way cloud infrastructure is deployed determines its accessibility and purpose. A public cloud is owned by a third-party provider and offers resources to the general public over the internet. A private cloud is provisioned for exclusive use by a single organization, offering greater control and security. A hybrid cloud connects public and private environments, allowing workloads to move seamlessly between them to balance cost, performance, and compliance requirements.
- Role of virtualization: Virtualization is the core enabling technology behind cloud computing. A hypervisor abstracts the underlying physical hardware, allowing multiple virtual machines with their own operating systems to run independently on a single physical host. This abstraction layer is what allows providers to pool resources, isolate tenants securely, and dynamically allocate compute power and memory to support rapid elasticity and on-demand provisioning.
Code Example
Bash
# List compute instances using a cloud provider CLI
cloud-cli compute instances list --region us-east-1
# Output shows instance IDs, types, and statesThis command demonstrates the on-demand self-service characteristic: users can instantly list and manage resources without human intervention from the provider.
Quick Revision
- Cloud computing is defined by five essential characteristics: on-demand self-service, broad network access, resource pooling, rapid elasticity, and measured service.
- These characteristics enable cost efficiency, scalability, and global reach for organizations.
- Cloud shifts IT from capital expense to operational expense, improving agility.
- Understanding these characteristics helps evaluate cloud services and choose appropriate solutions.