Cloud Computing (AD-702 (A)) - Unit 5 Short Notes

How unit 5 is examined

This unit compares open-source clouds (OpenStack, Eucalyptus, OpenNebula, CloudStack) and commercial clouds (AWS, Azure, Google Cloud); the marks sit in the OpenStack comparison and the AWS-Azure-Google comparison, with Azure features next.

Open Stack

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">High weight</span>

Definition. <mark>OpenStack is a free, open-source cloud operating system that controls large pools of compute, storage and networking resources in a data centre and offers them as IaaS through a dashboard and APIs.</mark>

Diagram.

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Key points.

1. OpenStack was started in 2010 by NASA and Rackspace and is released under the Apache 2.0 licence, so anyone can use and modify it free.
2. Nova is the compute service that creates and manages virtual machines on hypervisors such as KVM, Xen and VMware.
3. Swift stores objects (files) and Cinder gives block volumes to VMs, so storage is available in both styles.
4. Neutron provides networking (networks, subnets, routers, floating IPs) and Glance keeps the VM disk images.
5. Keystone handles authentication and the service catalogue, Horizon is the web dashboard, and Heat orchestrates stacks of resources.
6. Every service talks through REST APIs, so the design is modular and a provider installs only the services it needs.

Comparison of open-source clouds.

Answer frame. Open with the definition; draw the component diagram; describe OpenStack services in the order Nova, Swift/Cinder, Neutron, Glance, Keystone, Horizon; then give one paragraph each on OpenNebula and Eucalyptus (see their sections) and finish with the table; close with "OpenStack scales best, OpenNebula is simplest, Eucalyptus is AWS-compatible".

Asked: [14 marks] (Jun 2025) Explain and Compare OpenStack, OpenNebula and Eucalyptus as open-source cloud platforms.

Pitfall: Do not answer with OpenStack alone; the 14 marks need all three platforms and a table.

Eucalyptus

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Not asked since 2022</span>

Definition. <mark>Eucalyptus (Elastic Utility Computing Architecture Linking Your Programs To Useful Systems) is open-source software for building AWS-compatible private and hybrid clouds.</mark>

Key points.

1. The Cloud Controller (CLC) is the front end that exposes the EC2-compatible API and manages the whole cloud.
2. Walrus stores buckets and objects like Amazon S3, and the Storage Controller (SC) gives EBS-like block volumes.
3. Each cluster has a Cluster Controller (CC) that schedules VMs, and each machine runs a Node Controller (NC) that starts them on the hypervisor.
4. Because it copies AWS APIs, applications move between a Eucalyptus private cloud and AWS with little change.

Open Nebula

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Not asked since 2022</span>

Definition. <mark>OpenNebula is an open-source cloud management platform that manages virtualised data centres and builds private, public and hybrid IaaS clouds.</mark>

Key points.

1. A central front-end (the oned daemon) controls hosts, virtual machines, datastores and virtual networks.
2. It supports KVM, Xen and VMware hypervisors, so it is vendor-neutral.
3. Sunstone is its web GUI, and it also offers EC2-style and OCCI interfaces.
4. It is lightweight and easy to install, and can burst to public clouds such as AWS for hybrid use.

Apache Cloud Stack

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Not asked since 2022</span>

Definition. <mark>Apache CloudStack is an open-source IaaS platform, donated by Citrix to the Apache Foundation, that deploys and manages large networks of virtual machines.</mark>

Key points.

1. A management server controls everything and its resources are organised as Region, Zone, Pod, Cluster and Host.
2. Primary storage holds running VM disks and secondary storage holds templates, ISOs and snapshots.
3. It supports KVM, XenServer, VMware and Hyper-V hypervisors.
4. It has a web UI and REST API, plus EC2-compatible access, and is used by service providers to run public clouds.

Amazon (AWS)

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">High weight</span>

Definition. <mark>Amazon Web Services (AWS) is the world's largest commercial public cloud, launched in 2006, offering compute, storage, database and many other services on a pay-as-you-go basis.</mark>

Key points.

1. EC2 gives resizable virtual servers, and Lambda runs code without servers (serverless).
2. S3 provides object storage, EBS gives block disks, and RDS gives managed databases.
3. VPC gives private networks, IAM controls users and permissions, and CloudWatch monitors resources.
4. AWS is divided into Regions, each having several isolated Availability Zones, plus edge locations for CloudFront, so it has the widest global reach and Auto Scaling grows capacity on demand.
5. Pricing is pay-as-you-go per second or hour, with cheaper Reserved or Savings Plans (1-3 years) and Spot instances (unused capacity at large discounts), and a free tier for new users.

Comparison of commercial clouds.

Answer frame. Open by defining a commercial public cloud; briefly introduce the three providers; give the table and add one line per row on compute, storage, scalability and pricing; give one pricing example, such as Spot on AWS, Hybrid Benefit on Azure, sustained-use discount on Google; close by saying the choice depends on the workload.

Asked: [14 marks] (Jun 2025) How do Amazon AWS, Microsoft Azure, and Google Cloud differ in terms of features, scalability, and pricing?

Pitfall: Naming services without comparing pricing models loses the pricing marks.

Microsoft Azure

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Low weight</span>

Definition. <mark>Microsoft Azure is Microsoft's public cloud platform that provides IaaS, PaaS and SaaS services through Microsoft data centres worldwide.</mark>

Key points.

1. Compute: Virtual Machines, App Service and Functions run servers, web apps and serverless code.
2. Storage: Blob storage holds unstructured data, with Disk, File and Azure SQL Database for other needs.
3. Networking: Virtual Network, Load Balancer and VPN Gateway connect cloud and on-premises systems, giving strong hybrid support.
4. AI and analytics: Azure AI services, Machine Learning and Synapse are available.
5. Security: Azure Active Directory (Entra ID) gives identity and single sign-on, along with Key Vault and encryption.

Asked: [7 marks] (Dec 2024) Explain the major cloud features of Microsoft Azure.

Google cloud

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Not asked since 2022</span>

Definition. <mark>Google Cloud Platform (GCP) is Google's public cloud that offers IaaS, PaaS and data services running on the same infrastructure as Google Search and YouTube.</mark>

Key points.

1. Compute Engine gives VMs, App Engine is PaaS, and Google Kubernetes Engine (GKE) manages containers.
2. Cloud Storage holds objects, and BigQuery is a serverless data warehouse for analytics.
3. It is strong in AI and machine learning (Vertex AI, TensorFlow) and uses a fast private global network.
4. Billing is per second with automatic sustained-use discounts.

Last-minute revision

• OpenStack: Nova compute, Swift object, Cinder block, Neutron network, Glance images, Keystone identity, Horizon dashboard, Heat orchestration.
• OpenStack began in 2010 with NASA and Rackspace and uses the Apache 2.0 licence.
• Eucalyptus components: CLC, Walrus, CC, SC, NC; it is AWS EC2 and S3 compatible.
• OpenNebula is simple and lightweight, with a front-end, Sunstone GUI, and KVM, Xen and VMware support.
• CloudStack hierarchy: Region, Zone, Pod, Cluster, Host; donated by Citrix to Apache.
• AWS launched 2006; key services EC2, S3, EBS, RDS, Lambda, VPC, IAM, CloudWatch.
• AWS pricing: on-demand, Reserved or Savings Plans, Spot, free tier.
• Azure: VMs, Blob, Azure AD, strongest for Windows and hybrid use.
• Google Cloud: Compute Engine, BigQuery, GKE, sustained-use discounts.
• Scalability and market share: AWS first, Azure second, Google Cloud third.

Memory hooks

• OpenStack services "N-S-C-N-G-K-H": Nova, Swift, Cinder, Neutron, Glance, Keystone, Horizon.
• Eucalyptus "Walrus = S3": the walrus stores buckets.
• CloudStack ladder "R-Z-P-C-H": Region, Zone, Pod, Cluster, Host.
• Cloud strengths "AWS = Widest, Azure = Windows, Google = Data".

Coverage checklist

• Open Stack: Jun 2025 comparison of OpenStack, OpenNebula and Eucalyptus.
• Eucalyptus: covered (also in the comparison table).
• Open Nebula: covered (also in the comparison table).
• Apache Cloud Stack: covered.
• Amazon (AWS): Jun 2025 AWS, Azure and Google Cloud comparison.
• Microsoft Azure: Dec 2024 Azure features.
• Google cloud: covered (also in the comparison table).