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Chapter 5. Virtualization

Virtualization updates in Red Hat Enterprise Linux 6.5 include a number of bug fixes in areas such as live migration, error reporting, hardware and software compatibility. In addition, performance and general stability improvements have been implemented. For the most significant of these changes, see the sections below.

5.1. KVM

Improved Support For the VMDK Image File Format

Red Hat Enterprise Linux 6.5 includes a number of improvements to read-only support for Virtual Machine Disk, or VMDK, image file formats, including its subformats, as created by many VMware products.

Windows Guest Agent Fully Supported

The Windows guest agent is now fully supported and delivered with its own installer in the Supplementary channel together with virtio-win drivers.

Support for the VHDX Image File Format

Red Hat Enterprise Linux 6.5 includes read-only support for Hyper-V virtual hard disk, or VHDX, image formats, as created by Microsoft Hyper-V.

Native Support for GlusterFS in QEMU

Native Support for GlusterFS in QEMU allows native access to GlusterFS volumes using the libgfapi library instead of through a locally mounted FUSE file system. This native approach offers considerable performance improvements.

Support for Dumping Metadata of Virtual Disks

This low-level feature uses the newly introduced command option qemu-img map to create an index that allows a qcow2 image to be mapped to a block device via LVM. As a result, virtual machine images (with the virtual machine shutdown) can be accessed as block devices. This is useful for backup applications that are now able to read guest image contents without knowing the details of the qcow2 image format.

Enabling and Disabling CPUs in Linux Guests

With this update, it is possible to use the --guest option with the virsh setvcpus command. This enables or disables virtual CPUs (vCPUs) to set the specified number of vCPUs. Note, however, that this does not add or remove any vCPUs, and will fail if used to set more vCPUs than are currently available on the guest. In addition, to use this feature, the QEMU guest agent must be installed on your system.

Application-Aware freeze and thaw on Microsoft Windows with VSS Support on qemu-ga-win

VSS (Volume Shadow Copy Service) is a Microsoft Windows API that allows, among other things, the notification of applications for proper, consistent freeze and thaw operations. With this feature, snapshots taken while the virtual machine is running are consistent through the whole stack (from the block layer to the guest applications) and can be used for backup purposes. For more information, see the Virtualization Administration Guide

Application-Aware freeze and thaw on Linux Using qemu-ga Hooks

Similar to the Windows VSS version, application-consistent snapshots can be created with the use of scripts that attach to the QEMU guest agent running on the guest. These scripts can notify applications which would flush their data to the disk during a freeze or thaw operation, thus allowing consistent snapshots to be taken.

Conversion of VMware OVF and Citrix Xen Guests to KVM Guests

The virt-v2v conversion tool has been upgraded to an upstream version to support conversion of VMware Open Virtualization Format (OVF) and Citrix Xen guest conversion to KVM.

Increased KVM Memory Scalability

KVM virtual memory scalability in a single guest has been increased to 4TB.

Support of Volume Control from within Microsoft Windows Guests

Users can now fully control the volume level on Microsoft Windows XP guests using the AC'97 codec.

Opening Connections from a File

It is now possible to set up a remote-viewer session from a configuration file associated with a registered MIME type, for example, from the Red Hat Enterprise Virtualization Manager portal. A simple browser link can be used without the need for a browser-specific plug-in or multi-process communication.

Host and Guest Panic Notification in KVM

A new pvpanic virtual device can be wired into the virtualization stack such that a guest panic can cause libvirt to send a notification event to management applications. This feature is introduced in Red Hat Enterprise Linux 6.5 as a Technology Preview. Note that enabling the use of this device requires the use of additional qemu command line options; this release does not include any supported way for libvirt to set those options.

5.2. Microsoft Hyper-V

Microsoft Hyper-V Para-Virtualized Drivers

To enhance Red Hat Enterprise Linux support on Microsoft Hyper-V, Synthetic Video Frame Buffer Driver has been added to Red Hat Enterprise Linux 6.5. In addition, the signaling protocol between the host and the guest has been updated. For more information, see Virtualization Administration Guide

5.3. VMware

VMware Platform Drivers Updates

The VMware network para-virtualized driver has been updated to the latest upstream version.