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Red Hat Enterprise Virtualization: Overview of RHEV-M, RHEV-H and RHEL

Red Hat Enterprise Virtualization is a powerful and versatile server virtualization platform that’s often overshadowed by vSphere and Hyper-V. Because the underlying KVM hypervisor is integrated

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into the Linux kernel, Red Hat Enterprise Virtualization (RHEV) can sometimes offer superior cost, security and performance than other virtualization offerings. But to get the most out of RHEV, you must understand how it’s architected.  

The RHEV Manager, also known as the RHEV-M management console, is the core component of Red Hat’s server virtualization platform. It provides a Web interface for managing virtual machines (VMs) that are running on physical nodes.

The other important part of the RHEV environment is the nodes themselves, on which you host the VMs. Nodes can be configured with the  RHEV-H hypervisor or as Red Hat Enterprise Linux (RHEL) servers with a virtualization entitlement. Both types of nodes use KVM as the underlying hypervisor.

The RHEV-H hypervisor is the default choice when setting up a RHEV node. It’s a bare-metal hypervisor, containing just a subset of RHEL code for running virtual machines. As such, RHEV-H hosts are easier to maintain. Additionally, these hosts require less patching and effort to secure.

RHEV-H base file system is just more than 100 MB and runs in the memory, which prevents changes to the base image. This configuration also reduces the chance for human error when changes are made to the host.

Also, the RHEV-H node is secured by a dedicated Security-Enhanced Linux policy and a firewall that blocks all traffic, with the exception of traffic directed to the virtual machines and management traffic to the hypervisor.

In addition to RHEV-H nodes, the RHEV Manager also supports RHEL hosts running KVM. This capability makes it easier to deploy RHEV in an existing RHEL environment.

The importance of VDSM for Red Hat Enterprise Virtualization
The RHEV-M management console gathers information about and interacts with invidual nodes using the Virtual Desktop Server Manager (VDSM). VDSM is a management agent that resides on the node, and it facilitates communication between the management console and hosts. VDSM also allows RHEV-M to manage the virtual machines and storage, and collects performance statistics that pertain to hosts and guests.

But VDSM cannot function when libvirt is active. Libvirt is the library that manages the RHEL virtual environment. So if you’re planning a RHEV implementation, make sure that libvirt is deactivated on every node that RHEV manages. Otherwise, neither libvirt nor VDSM will function properly.

The central repository for RHEV
Another vital component of a RHEV infrastructure is the central storage repository. It consists of two main parts:

  • the data storage domain, which is used for storing VM images, templates and snapshots; and
  • the ISO storage domain, which houses the ISO files used for virtual machine installations.

RHEV does not mandate any specific storage requirements.

After installing RHEV-M and configuring the virtual hosts, you are all set. Red Hat Enterprise Virtualization contains all of the advance features that are typically found in a virtual environment, including high availability, load balancing and live migration.

In an upcoming article, you'll learn how to build your own Red Hat Enterprise Virtualization test lab.

This was first published in January 2012

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