Xen 4.0 virtualization ups the ante with performance, scalability, and availability

The new Xen 4.0 hypervisor adds more than two dozen new features to make virtualization suitable for all types of workloads

Xen.org has launched a new version of the open source Xen hypervisor, and while the new virtualization platform may not yet have reached complete feature parity with its VMware vSphere competitor, the updated hypervisor has now caught up in version numbering with vSphere as Xen.org pushes out the door the latest 4.0 version of Xen.

Xen 4.0 follows closely on the heels of Xen 3.4.2, released back in November 2009. Xen.org is calling the new release "the most advanced open source hypervisor software available," adding that the release is the collective effort of a global development team representing more than 50 leading technology vendors, universities, and virtualization experts. The group is claiming that Xen 4.0 will offer substantial improvements for both on-premise and cloud computing workloads.

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"The new advancements in Xen 4.0 will bring cloud and virtualization to new levels, and Citrix is dedicated to applying them across our entire stack -- from desktop virtualization to cloud computing," said Simon Crosby, CTO of Citrix Systems' data center and cloud division.

For added performance and scalability on the host layer, the new Xen 4.0 hypervisor now spans 128 physical CPUs across the host server and can address up to 1TB of physical main system memory. In the guest environment, virtual machines running on top of Xen 4.0 can now be allocated to up to 128 virtual CPUs (although memory capacities for virtual machines were not found).

Further improvements include taking advantage of new reliability, availability, and serviceability (RAS) features found in the new Intel Xeon (Nehalem-EX) and AMD Opteron 6000 processors. Users can now hot-plug CPUs and memory in a physical server without having to shut down the hypervisor or its virtual machines. Users can also now resize virtual hard disks without requiring a reboot or shutting down the virtual machine, which is another great time-saving feature.

Xen 4.0 adds more than two dozen other new enhancements to the hypervisor, the most significant of which is arguably the addition of fault tolerance thanks to Project Remus. The hypervisor now includes support for live transactional synchronization of virtual machine states between physical servers as a basic component, enabling administrators to guarantee a high degree of service reliability without requiring additional software solutions. The new fault-tolerance feature enables a virtual machine on one physical server to be mirrored by a virtual machine on another physical server. If one physical server goes down, the backup virtual machine would continue running on the second server without any noticeable interruption of the workload to the user.

Another advanced addition is something called Netchannel2, which takes full advantage of significant advancements made in networking hardware such as SMART NICs with multi-queue and SR-IOV functionality. This provides virtualization infrastructures with superior data processing capabilities, allowing high levels of network traffic to flow into a Xen-based virtual machine. With it, a single NIC can present itself as a separate network adapter to individual virtual machines.

Snapshots and cloning of virtual hard disks (VHDs) has also been improved with support for the Blktap2 driver. The new VHD implementation in Xen 4.0 delivers high-performance virtual machine snapshots and cloning features as well as the ability to do live virtual disk snapshots without stopping a virtual machine process.

Xen 4.0 also adds new memory enhancements. New algorithms such as Transcendent Memory and Page Sharing have been introduced to enhance the performance and capabilities of the hypervisor memory operations. Transcendent Memory, or tmem, provides a new approach for improving the utilization of physical memory in a virtualized environment by claiming underutilized memory in a system and making it available where it is needed most. It is said that tmem can be thought of as a fast RAMdisk that is useful when real RAM is in short supply and is accessible only via a quirky copy-based interface. Xen 4.0 also adds an initial implementation of memory page-sharing. This allows multiple virtual machines to share common memory pages, thereby reducing overall memory consumption.

The updated hypervisor has also increased performance by improving certain pass thru technologies. Xen 4.0 has improved its virtual I/O by making better use of the accelerated I/O virtualization techniques found within the Intel Xeon VT-d and AMD Opteron IOMMU features. It also offers high-performance graphics support by using VGA primary graphics card pass thru to gain direct access to the graphics card GPU from the guest operating system.

Being able to run performance and network-intensive and latency-sensitive applications mean that almost any workload can now operate within a virtual machine environment. As processor and hypervisor improvements continue to be made, administrators will be able to look across the entire data center and say that almost any application is now a good candidate for virtualization as performance limitations continue to get thrown out of the proverbial window.

A full list of all the new features and enhancements in Xen 4.0 can be found on the Xen community Website.

This article, "Xen 4.0 virtualization ups the ante with performance, scalability, and availability" was originally published at InfoWorld.com. Follow the latest developments in business technology news and get a digest of the key stories each day in the InfoWorld Daily newsletter and on your mobile device at infoworldmobile.com.

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