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Virtualization-enhanced chips may rev up performance

Intel and AMD promise virtualization will lead to better performance with their enhanced processors.

Hardware vendors are making the case for enhanced virtualization by developing special processors that work hand-in-glove with software to boost performance.

Virtualization software allows a single computer to create several virtual, rather than actual, versions of a computing environment. With virtualization, one physical machine can host multiple virtual versions of an operating system and run them simultaneously.

But new enhanced processors from chipmakers Advanced Micro Devices Inc., located in Sunnyvale, Calif., and Santa Clara, Calif.-based Intel Corp. could change virtualization from a software-only technology to one in which software and hardware work together for a more coordinated result.

"When the VM addresses the hardware directly, we won't see a performance difference between a VM and a physical server."
Chris Wolf
Virtualization Consultant

This type of chip-level support for virtualization leads to performance and reliability gains and may push more enterprises to adopt virtualization in their IT shops, said Chris Wolf, a virtualization consultant and co-author of Virtualization: From the Desktop to the Enterprise (Apress).

"The latency has always scared some shops from running a real high-performance application, such as an Oracle server, inside a Virtual Machine," said Wolf. "But when the VM [virtual machine] addresses the hardware directly, we won't see a performance difference between a VM and a physical server."

Software companies like VMware Inc. and Microsoft have created hypervisors -- the virtual management layer that divides up access to hardware resources. The hypervisor gives each instance of an OS a virtual processor and selectively grants virtual machines access to physical processor resources, like memory and I/O, as needed. Each virtual OS thinks it's running on its own system, but it doesn't have direct access to the hardware.

Now both major chipmakers have baked special virtualization extensions into their processors that simplify the hardware layer and make the process more efficient than with software alone. The new architecture, called Intel VT and AMD-V, encodes the virtualization process at the hardware level and defines the characteristics of each VM, including processor, memory and I/O resources.

More bang for the buck

Hardware-level support for virtualization has been demonstrated to improve performance from virtualization software. Research from USENIX, the Advanced Computing Systems Association, found that running a system in a fully virtualized environment increases service latency by 2 to 2.5 times over levels in a non-virtualized environment.

"Running virtual software forces a system to make certain compromises to run multiple OSes at the same time," according to Tony Iams, vice president and senior analyst for Ideas International Inc. in Rye Brook, N.Y.

Virtualization-enhanced chips will reduce the overhead of the virtualization process by eliminating the need for the software to do binary translation, said David Marshall, co-author of Advanced Server Virtualization: VMware and Microsoft Platforms in the Virtual Data Center.

"The virtualized machine will run as well as it would on bare metal itself."
Margaret Lewis
Commercial Software StrategistAMD

"Virtualization-enhanced processors allow applications to run without modification and allow for unmodified guest operating systems support," said Marshall. "They make virtualization solutions better by eliminating some of the need for complex software workarounds or trickery."

As a result, more OSes can run simultaneously on a system and share the hardware, according to Margaret Lewis, commercial software strategist with AMD. "The extensions take away some of the overhead and allow for the software to spoof this environment more simply," said Lewis. "Now we'll see near-native performance levels. The virtualized machine will run as well as it would on bare metal itself."

AMD is also planning to release I/O virtualization support in processors, which will make VMs interact with attached devices, such as printers, more transparently, she said.

Chips ready to go

AMD-V is already available in desktop and mobile versions of AMD processors. AMD said it expects to make an announcement next month on plans to release a virtualization-enhanced version of Operton, the AMD server chip. AMD I/O virtualization-enabled chip sets will likely hit the market in 2007, the company said.

Intel has been shipping server and client processors with Intel VT since November. The company released specifications for its own virtualization technology for directed I/O, Intel VT-d, in February but has not indicated yet when chips with that technology will be available.

Software vendors are just starting to test the waters with products that take advantage of the virtualization-enhanced chips. VMware has released versions of VMware Player and VMware Workstation and beta releases of VMware Server and VMware ESX Server with experimental support for the processors.

Microsoft's Virtual Server 2005 R2 SP1, now in beta, offers support for Intel VT only. The second beta of the product will support AMD-V and is scheduled for release at the end of this year. Open source vendor XenSource Inc. offers a hypervisor product, Xen 3.0.2, that supports both AMD-V and Intel VT.

Industry analysts, like Marshall, say the processing technology needs to mature before software makers begin to take advantage of them. "The benefit will become more evident when the virtualization hypervisors and platforms take full support of the Intel VT or AMD-V technology," said Marshall. "I don't think the true benefit is there yet because the software has to now catch up to the hardware."

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