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What is OpenStack?

A comprehensive guide to OpenStack architecture and components

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Understanding OpenStack

OpenStack is an open-source cloud computing platform that enables organizations to build and manage their own private and public cloud infrastructure. It provides a collection of interrelated services that control pools of processing, storage, and networking resources, all managed through a dashboard or API. OpenStack allows users to deploy virtual machines and other instances that handle different tasks for managing a cloud environment on the fly.

What is OpenStack?

The Cloud Operating System

OpenStack is often referred to as the "Linux of the cloud" because it provides an open alternative to proprietary cloud platforms:

  • Infrastructure as a Service (IaaS): Provides virtualized computing resources similar to AWS, GCP, and Azure
  • Open Source Foundation: Developed by a global community of thousands of contributors
  • Modular Architecture: Composed of dozens of projects with specific functions that work together
  • API-Driven: All functions can be controlled programmatically through RESTful APIs

OpenStack bridges the gap between public cloud convenience and the control of on-premises infrastructure, making it ideal for organizations seeking control, customization, and cost-effectiveness in their cloud strategy.

graph LR A[OpenStack Cloud Platform] A --> B[Compute] A --> C[Storage] A --> D[Networking] A --> E[Identity] A --> F[Dashboard] A --> G[Additional Services] B --> B1[Nova] C --> C1[Cinder] C --> C2[Swift] D --> D1[Neutron] E --> E1[Keystone] F --> F1[Horizon] G --> G1[Heat] G --> G2[Ceilometer] G --> G3[Trove] %% 스타일은 반드시 마지막에 깔끔하게 정의 style A stroke:#333,stroke-width:1px,fill:#f5f5f5 style B stroke:#333,stroke-width:1px,fill:#a5d6a7 style C stroke:#333,stroke-width:1px,fill:#64b5f6 style D stroke:#333,stroke-width:1px,fill:#ffcc80 style E stroke:#333,stroke-width:1px,fill:#ce93d8 style F stroke:#333,stroke-width:1px,fill:#ef9a9a style G stroke:#333,stroke-width:1px,fill:#b39ddb


Core Components and Architecture

OpenStack's modular architecture consists of various components that work together to provide a complete cloud platform. Each component is a separate project with its own development team, but they are designed to integrate seamlessly while addressing specific cloud infrastructure needs.

Core Services

Component Code Name Equivalent Description
Compute Nova AWS EC2
  • Manages the lifecycle of compute instances (virtual machines)
  • Handles scheduling, creation, and termination of VMs
  • Supports multiple hypervisors (KVM, QEMU, Hyper-V, VMware)
  • Scales horizontally across standard hardware
Networking Neutron AWS VPC
  • Provides Software-Defined Networking capabilities
  • Manages networks, subnets, routers, and security groups
  • Supports advanced networking features like VLANs, VPNs, and load balancing
  • Implements network isolation between tenants
Block Storage Cinder AWS EBS
  • Provides persistent block storage for compute instances
  • Supports multiple storage backends (LVM, Ceph, NFS)
  • Offers features like snapshots, backups, and volume types
  • Allows attaching/detaching volumes to/from instances
Object Storage Swift AWS S3
  • Highly available, distributed object storage
  • Stores and retrieves arbitrary unstructured data
  • Built for scale and durability
  • Includes built-in redundancy and fault tolerance
Identity Keystone AWS IAM
  • Provides authentication and authorization for all OpenStack services
  • Implements a token-based system for API access
  • Manages user accounts, roles, and project associations
  • Supports integration with external identity providers (LDAP, Active Directory)

Supporting Services

Additional Core Components

Beyond the fundamental infrastructure services, OpenStack includes several supporting components:

  • Image Service (Glance): Stores and retrieves virtual machine disk images
  • Dashboard (Horizon): Provides a web-based interface for managing OpenStack resources
  • Orchestration (Heat): Automates the deployment of infrastructure using templates
  • Telemetry (Ceilometer): Collects measurements for billing, benchmarking, and scaling
  • Database Service (Trove): Provides database-as-a-service capabilities

Architectural Overview

graph LR A[Users/API Clients] --> B[API Gateway] B --> C[Identity Service - Keystone] B --> D[Dashboard - Horizon] B --> E[Compute - Nova] E --> E1[Hypervisors] B --> F[Networking - Neutron] F --> F1[Network Infrastructure] B --> G[Block Storage - Cinder] G --> G1[Storage Backend] B --> H[Object Storage - Swift] H --> H1[Object Storage Nodes] B --> I[Image Service - Glance] I --> I1[Image Repository] B --> J[Orchestration - Heat] C --> K[Message Queue] E --> K F --> K G --> K I --> K J --> K C --> L[Database] E --> L F --> L G --> L I --> L J --> L style A stroke:#333,stroke-width:1px,fill:#f5f5f5 style B stroke:#333,stroke-width:1px,fill:#a5d6a7 style C stroke:#333,stroke-width:1px,fill:#64b5f6


Deployment Models and Use Cases

OpenStack offers flexibility in deployment, making it suitable for various organization sizes and use cases. From small development environments to large-scale public clouds, OpenStack can be tailored to meet specific requirements while providing a consistent API experience.

Deployment Models

Model Characteristics Best For
Private Cloud
  • Deployed within an organization's firewall
  • Dedicated to a single organization
  • Complete control over infrastructure and data
  • Customizable to specific requirements
  • Enterprises with regulatory compliance needs
  • Organizations with consistent, predictable workloads
  • Environments requiring specific security controls
  • Companies with existing datacenter investments
Public Cloud
  • Operated by service providers
  • Multi-tenant environment
  • Pay-as-you-go model
  • Standardized service offerings
  • Service providers offering cloud services
  • Regional cloud providers
  • Organizations offering specialized cloud services
  • Telecommunications companies expanding to cloud
Hybrid Cloud
  • Combination of private and public clouds
  • Workload portability between environments
  • Unified management interface
  • Flexible resource allocation
  • Organizations with variable workloads
  • Companies with burst capacity requirements
  • Businesses with disaster recovery needs
  • Enterprises in transition to cloud architecture

Common Use Cases

Real-World Applications

OpenStack has been successfully deployed across various industries:

  • Scientific Research: High-performance computing clusters and data processing
  • Telecommunications: Network function virtualization (NFV) and edge computing
  • Financial Services: Secure, compliant infrastructure for sensitive workloads
  • Healthcare: HIPAA-compliant private clouds for patient data
  • Media & Entertainment: Rendering farms and content delivery networks
  • Government: Secure cloud environments for public services
  • Education: Research computing and student lab environments


Implementation Considerations

While OpenStack offers tremendous flexibility, its implementation requires careful planning. Understanding the advantages, challenges, and resource requirements is essential for a successful deployment that meets organizational needs.

Advantages and Challenges

graph LR A[OpenStack Considerations] A --> B[Advantages] A --> C[Challenges] B --> B1[Open Source] B --> B2[Flexibility] B --> B3[Vendor Independence] B --> B4[Community Support] C --> C1[Complexity] C --> C2[Technical Expertise] C --> C3[Resource Requirements] C --> C4[Maintenance Overhead] style A stroke:#333,stroke-width:1px,fill:#f5f5f5 style B stroke:#333,stroke-width:1px,fill:#a5d6a7 style C stroke:#333,stroke-width:1px,fill:#ef9a9a
Advantages Challenges
  • No Vendor Lock-in: Freedom to change components and providers
  • Cost Savings: No licensing fees for the platform itself
  • Customization: Ability to modify code for specific needs
  • Innovation: Access to cutting-edge features from the community
  • Diverse Hardware Support: Works with a wide range of equipment
  • Steep Learning Curve: Requires specialized knowledge
  • Complex Deployment: Many interconnected components
  • Operational Overhead: Significant maintenance requirements
  • Performance Tuning: Requires expertise for optimization
  • Upgrade Complexity: Can be challenging to move between versions

Resource Requirements

Hardware Considerations

OpenStack's resource requirements vary based on scale, but some general guidelines include:

  • Minimum Production Deployment: At least 3 controller nodes and 2+ compute nodes
  • Controller Nodes: 8+ CPU cores, 16+ GB RAM, redundant NICs
  • Compute Nodes: CPU with virtualization support, adequate RAM for guest VMs
  • Storage: Dedicated storage network recommended, high-performance disks for Cinder
  • Networking: Multiple network interfaces, 10GbE recommended for production
  • High Availability: Load balancers, database clustering, redundant message queues

For production environments, running on minimal hardware is strongly discouraged due to performance and reliability concerns.

High Availability Architecture

# Example High Availability Configuration
infrastructure:
  controllers:
    - controller1:
        role: primary
        services: [keystone, horizon, glance, placement]
        ip: 10.0.0.11
    - controller2:
        role: secondary
        services: [keystone, horizon, glance, placement]
        ip: 10.0.0.12
    - controller3:
        role: secondary
        services: [keystone, horizon, glance, placement]
        ip: 10.0.0.13
  
  network:
    - network1:
        services: [neutron-server, neutron-dhcp, neutron-l3]
        ip: 10.0.0.21
    - network2:
        services: [neutron-server, neutron-dhcp, neutron-l3]
        ip: 10.0.0.22

  compute:
    - compute1:
        hypervisor: kvm
        ip: 10.0.0.31
    - compute2:
        hypervisor: kvm
        ip: 10.0.0.32
    - compute3:
        hypervisor: kvm
        ip: 10.0.0.33

shared_services:
  database:
    type: galera
    nodes: [10.0.0.11, 10.0.0.12, 10.0.0.13]
    vip: 10.0.0.10
  
  messaging:
    type: rabbitmq
    nodes: [10.0.0.11, 10.0.0.12, 10.0.0.13]
    vip: 10.0.0.15
  
  load_balancing:
    type: haproxy
    nodes: [10.0.0.11, 10.0.0.12, 10.0.0.13]
    vip_management: 10.0.0.20
    vip_public: 203.0.113.10


Getting Started with OpenStack

For those interested in exploring OpenStack, there are several approaches to get started—from simple development environments to full production deployments. The right approach depends on your goals and available resources.

Deployment Options

Method Description Best For
DevStack
  • Single-machine deployment
  • Script-based installation
  • Minimal hardware requirements
  • Easy setup and teardown
  • Developer environments
  • Learning and exploring OpenStack
  • Testing new features
  • CI/CD pipelines
Packstack
  • Red Hat-based deployment
  • Single node or small clusters
  • Package-based installation
  • More production-like than DevStack
  • Small proof-of-concept environments
  • Lab setups
  • Training environments
  • Small-scale deployments
Kolla-Ansible
  • Container-based deployment
  • Supports multi-node setups
  • Highly configurable
  • Simplified upgrades
  • Production deployments
  • Organizations with container expertise
  • Environments requiring frequent upgrades
  • Mature OpenStack deployments
TripleO
  • OpenStack on OpenStack
  • Enterprise-grade deployment
  • Highly available architecture
  • Complex but powerful
  • Large-scale production environments
  • Telco-grade deployments
  • Organizations with OpenStack expertise
  • Mission-critical workloads

Basic DevStack Setup



Key Points

💡 OpenStack Essentials
  • Core Functionality
    - Provides infrastructure as a service (IaaS) capabilities
    - Modular design with specialized components for compute, storage, and networking
    - Open-source alternative to proprietary cloud platforms
    - API-driven architecture for automation and integration
  • Deployment Considerations
    - Suitable for private, public, and hybrid cloud models
    - Requires significant technical expertise
    - Hardware requirements vary based on intended scale
    - Several deployment tools available for different needs
  • Business Benefits
    - Eliminates vendor lock-in concerns
    - Reduces licensing costs
    - Provides complete control over cloud infrastructure
    - Enables customization for specific organizational requirements
    - Supports integration with existing infrastructure


References