Virtualization.pdf

Definition

Virtualization refers to technologies designed to provide a layer of abstraction between hardware and software layers. This abstraction simplifies interactions, enabling more efficient use of resources by creating virtual representations of physical resources such as servers, storage, and networks.

Key Domains of Virtualization

• Server Virtualization:
  • Involves converting a physical server into multiple virtual servers.
  • The primary domain of virtualization, allowing for server consolidation, which reduces the number of physical servers by running multiple virtual machines (VMs) on a single server.
• Virtual Machines (VMs):
  • A VM is a software-based emulation of a physical server, consisting of an operating system and applications.
  • VMs are isolated from one another and use emulation to mimic hardware components (CPU, memory, NIC).
  • Drivers within the VM allow communication between the operating system, applications, and the emulated hardware.
• Hypervisors:
  • Hypervisors, also known as Virtual Machine Monitors (VMM), enable multiple operating systems or VMs to run on a single physical server.
  • Type 1 (Bare-metal): Installed directly on hardware, positioned between the hardware and VMs.
  • Type 2 (Hosted): Installed on top of an existing operating system, allowing an additional OS to run in a virtual environment on top of the host OS.

Key Technologies and Concepts

• High Availability:
  • Continuously monitors virtual machines within a virtual resource pool for hardware failures, ensuring reliability.
• Fault Tolerance:
  • Prevents service interruptions by creating redundant copies of VMs that can take over in case of failure.
• Live Migration:
  • The process of transferring running virtual machines from one physical server to another with minimal downtime, typically used for load balancing or server maintenance.
• Distributed Resource Scheduler (DRS):
  • Balances server capacity by dynamically allocating resources among virtual machines based on utilization and predefined rules, prioritizing critical applications.
• Distributed Power Management (DPM):
  • Optimizes power consumption by consolidating VMs onto fewer servers during low demand periods and powering off unused servers.

Types of Virtualization

• Server Virtualization:

  • Full Virtualization: The hypervisor acts as the hardware abstraction layer, hosting isolated VMs .
  • Para-Virtualization: Specially modified operating system(s) are installed on top of the hypervisor to host multiple guest operating systems. One of the differences with full virtualization is that the guest operating systems are aware that they are running in a virtualized environment
  • OS Partitioning: Divides a single operating system into multiple isolated partitions, each functioning as an independent server.

• Application Virtualization:

  • Isolates applications from the operating system, allowing them to be packaged and distributed independently.
  • Sandboxing and Application Streaming are common types, enabling secure and flexible application deployment.

• Desktop Virtualization:

  • Separates the desktop environment from the physical device, allowing remote access to virtual desktops hosted on a central server.

• Storage Virtualization:

  • Pools physical storage from multiple devices into a single virtualized environment, simplifying management and improving utilization.

• Network Virtualization:

  • Combines network resources into a single virtual network, enhancing flexibility and scalability.
  • Includes technologies like VLAN (Virtual Local Area Network), VIP (Virtual IP), and VPN (Virtual Private Network).

  

Disaster Recovery and Virtualization