Xen 4.0 Virtualization Hypervisor Offers Scalability, Availability Upgrades

Xen.org is rolling out the latest release of the Xen virtualization hypervisor with more than two dozen new features, including fault-tolerance capabilities, support for reliability and availability features in new high-end chips from Intel and AMD, and greater memory and networking capabilities.

Xen.org is unveiling the latest release of its open-source Xen hypervisor, boosting the performance, scalability and availability of the virtualization technology.

Xen 4.0, introduced April 13, offers a host of new features designed to address demands coming from enterprises and the growth of cloud computing, according to Ian Pratt, founder and chairman of Xen.org.

Included in the more than 30 new features are fault-tolerance capabilities. Xen, like other virtualization hypervisors, enabled businesses to migrate virtual machines from one physical server to another for planned outages. However, it became more problematic when the outages were unplanned, Pratt said.

The new fault-tolerant feature enables a VM on one physical machine to be mirrored by a VM on another physical server, he said. Should one physical server go down, then the backup VM on the second server would continue running the workload with no interruption from the user's perspective.

"The new thing here is to ... have the ability to keep a second [VM] in sync," Pratt said in an interview. "[In the event of an outage], everything just seamlessly switches over to the other machine."

Many of the high-end databases and similar applications designed for clustered environments have some degree of protection, he said. However, the fault-tolerance capabilities in Xen 4.0 could help with other applications, such as typical e-mail servers.

The enhanced hypervisor also includes support for the myriad RAS (reliability, availability and serviceability) features in Intel's high-end Xeon 7500 "Nehalem EX" processors and Advanced Micro Devices' Opteron 6000 "Magny-Cours" chips, Pratt said.

Both processor families, introduced in late March, are the highest-performing x86 processors unveiled by the chip makers. Intel officials have said they are aiming their four- to eight-core processors at the high end of the server market, targeting workloads that traditionally have run on RISC systems or mainframes.

Contributing are the more than 20 RAS features inside the Xeon 7500 chips that until now were normally found in RISC processors, including MCA Recovery error correction, aimed at reducing data corruption and improving reliability.

Xen 4.0 support of the RAS features in the new chip platforms comes from Xen.org's close working relationship with the chip vendors, Pratt said. The group talks with chip and chipset makers, as well as OEMs, about what it would like to see in hardware five years out to dovetail with what is being done with Xen, he said.

Xen 4.0, through its NetChannel2 feature, also takes advantage of the smart NICs (network interface cards) that are being built to create virtualized environments that offer improved data processing capabilities. At the Intel Developer Forum in September 2009, Intel and Citrix Systems set up a demonstration showing high levels of network traffic coming into a VM running on Xen, something that could not have been done without smart NICs, Pratt said.

Being able to run such network-intensive and latency-sensitive applications means that essentially any workload can run in a virtualized environment, he said.

"Now it's almost possible to say that there are no apps out there that are not good for virtualization," Pratt said. "Now you can look at everything in the data center [as candidates for VMs]."

Xen 4.0 also includes a number of new memory enhancements, such as Transcendent Memory, which removes the pitfalls inherent when guest operating systems use spare memory available on physical servers, he said.

Before, the nature of the spare memory was hidden from the guest OS, so if the other software needed that memory, performance would nosedive.

With Transcendent Memory, the use of the spare memory is more upfront, letting IT administrators know, for example, if the memory has been used in a dynamic fashion, and letting them decide whether they want to try to use that memory.

A full list of the features in Xen 4.0 can be found at the Xen Community Website.

Pratt said along with the new features in Xen 4.0, the Xen Community and other open-source projects have spent the past year looking to make the Xen hypervisor platform more standardized in two areas-desktops and laptops, and cloud computing.

The goal is to create Xen-based turnkey offerings with a more complete and standard software stack that businesses can more easily implement, he said.

Pratt said he expects more news to come out of that effort in the coming weeks and months.