1.4. Hardware Virtualization Layer¶

1.4.1. Hardware Virtualization Basics¶

Virtuozzo Hybrid Server is based on the concept of hardware virtualization. Hardware virtualization has a base layer—a hypervisor. This layer is loaded directly on the bare server and acts as an intermediary between the server hardware and virtual machines. To allocate hardware and resources to virtual machines, Virtuozzo Hybrid Server virtualizes all hardware on the server. Once virtualized, hardware and resources can be easily assigned to virtual machines. With its virtual hardware, a virtual machine runs its own complete copies of an operating system and applications.

The following diagram shows the basic architecture of hardware virtualization.

Specifically, Virtuozzo Hybrid Server uses the KVM/QEMU hypervisor and manages virtual machines via the libvirt API.

Hardware virtualization enables you to:

• Create multiple virtual machines with different operating systems on a single physical host.

• Run multiple guest operating systems and their applications simultaneously on a single physical host without rebooting.

• Consolidate and virtualize the computing environment, reduce hardware costs, lower operating expenses, and increase productivity.

• Use open APIs and SDK for integration with in-house and third-party applications.

1.4.2. Virtuozzo Virtual Machines¶

From the standpoint of applications and virtual machine users, each virtual machine (VM) is an independent system with an independent set of virtual hardware. This independence is provided by the Virtuozzo Hybrid Server hardware virtualization layer. The main features of the virtualization layer are the following:

• A virtual machine resembles and works like a regular computer. It has its own virtual hardware. Software applications can run in virtual machines without any modifications or adjustment.

• Virtual machine configuration can be changed easily (e.g., adding new virtual disks or increasing RAM).

• Virtual machines are fully isolated from each other (file system, processes, sysctl variables) and the Virtuozzo Hybrid Server host.

• A virtual machine can run any supported guest operating system. The guest OS and its applications are isolated inside a virtual machine and share physical hardware resources with other virtual machines.

1.4.3. Virtual Machine Hardware¶

A Virtuozzo virtual machine works like a usual standalone computer.

By default, virtual machines are created with the following virtual hardware:

• 1 VirtIO SCSI HDD, expanding

• 1 CD-ROM (IDE for Windows and Debian guests, VirtIO SCSI for Linux guests except Debian)

• 1 VirtIO network adapter, bridged

• 32MB video card

Other hardware added to a default VM may depend on the chosen distribution (see Creating Virtual Machines).

The complete range of virtual hardware a virtual machine can have is provided in the table below.

1.4.4. Virtual Machine Files¶

A virtual machine has at least two files: a configuration file (PVS file) and a hard disk image file (HDD file). It can also have additional files: a file for each additional virtual hard disk and output files for virtual ports. By default, the virtual machines files are stored in the /vz/vmprivate/<UUID> directory on the Virtuozzo Hybrid Server server.

The list of files related to a virtual machine is given in the table below:

1.4.5. Support of Virtual and Real Media¶

This section lists the types of disks that can be used by Virtuozzo virtual machines and provides the information about basic operations you can perform on these disks.