Virtualization Technology is a method of abstracting physical resources (such as servers, networks, memory, and storage) to create logical resources, allowing users to manage and use these resources more efficiently. Virtualization breaks the limitations of physical devices, enabling multiple operating system instances to run on a single piece of hardware, thus improving resource utilization and flexibility.
Main Applications of Virtualization include:
- Memory Virtualization: Allows multiple virtual machines (VMs) to share physical memory.
- Disk Virtualization: Abstracts data storage through virtual disk files.
- Network Virtualization: Connects VMs to physical networks via virtual switches.
Types of Server Virtualization:
- Hosted Architecture: Installed as an application on an existing operating system, offering good compatibility but lower performance.
- Bare Metal Architecture: Directly installed on the hardware, providing better performance and support for advanced features.
Advantages of Virtualization
- Maximized Resource Utilization: Splits a physical server into multiple VMs, increasing resource efficiency.
- Ease of Migration and Protection: VMs exist as files, making migration and backup straightforward.
- Hardware Independence: VMs are not tied to specific hardware, enhancing flexibility.
- Advanced Features: Supports live migration, high availability, automatic resource allocation, and more.
Resource Sharing in Virtualized Environments
- CPU Virtualization: Implements multitasking through virtual CPUs (vCPUs).
- Memory Virtualization: Managed by the virtual machine kernel (vmkernel), supports memory optimization techniques.
- Network Virtualization: Connects VMs to physical networks via virtual switches.
- Storage Virtualization: Achieves shared storage through virtual disk files (vmdk).
vSphere Infrastructure Principles
- vSphere: VMware’s virtualization platform, supporting private, public, and hybrid cloud environments.
- ESXi: The core component of VMware, installed directly on hardware, manages VM resources.
- vCenter Server: Centralizes management of multiple ESXi hosts, providing advanced features like vMotion and DRS.
Management of ESXi Hosts
- Independent Management: Direct access to ESXi hosts, suitable for initial configuration and troubleshooting.
- vCenter Management: Unified management of multiple ESXi hosts through vCenter Server, offering advanced features and management interfaces.
Basic Concepts of Virtual Machines
- Virtual Machine: A logical computer consisting of a set of files, including configuration files (.vmx), disk files (.vmdk), swap files (.vswp), etc.
- Templates: Master copies of VMs used for rapid deployment of new VMs.
- Cloning: Creates an exact copy of a VM, supporting operations while the VM is powered on or off.
Types of Virtual Machine Migrations
- Cold Migration: Migrates a powered-off VM.
- Hot Migration: Migrates a powered-on VM, including vMotion and Storage vMotion.
Virtual Machine Snapshots
- Snapshots: Record the state of a VM at a specific point in time, useful for testing, backups, and quick recovery.
- Working Principle: Creates an incremental disk to retain the VM’s state at the time of the snapshot. Restoring a snapshot deletes the incremental disk.
VMware’s Availability and Scalability
- HA (High Availability): Automatically restarts VMs on other hosts in case of a host failure, ensuring business continuity.
- FT (Fault Tolerance): Provides zero downtime and zero data loss with high availability.
- DRS (Distributed Resource Scheduler): Dynamic load balancing, intelligently allocates resources, and improves resource utilization.
Summary
Virtualization technology abstracts physical resources to enhance resource utilization and flexibility, supporting various advanced features and widely applied in cloud computing environments. vSphere and ESXi provide powerful virtualization management tools, helping organizations achieve efficient and reliable IT infrastructure.