The Benefits of Data Center Virtualization

How Hardware Is Helping Server, Desktop System Virtualization

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By: Daniel Dern (7/29/2010)

Today’s CPUs, motherboards, even BIOS are improving virtualization performance. Computer virtualization involves one or more virtual machines (VMs) emulating a hardware environment under a virtual machine monitor (VMM), a.k.a. hypervisor. It’s compute-intensive, to say the least. Modern computer virtualization began as software, but hardware is getting into the act – and, in the process, improving performance, including the number of VMs a host machine can run concurrently, and the effective cost per VM. Faster, multicore processors make a difference, of course; and so does more RAM. But these aren’t enough. Fortunately, today’s hardware includes a growing number and range of features specifically aimed at improving virtualization performance. Improved performance isn’t just execution speed; it also impacts the number of concurrent virtual machines a system can run. The security, reliability and flexibility of VMs are an issue too, such as the ability to move a VM from one hardware environment to another. The earliest hardware assists for virtualization were Intel’s Extended Page Table (EPT) and AMD’s Rapid Virtualization Indexing (RVI) technologies, which let the hardware manage paging for a virtual machine, reducing virtualization’s overhead. “With the introduction of EPT and RVI, most of the burden of managing the paging for a virtual machine and keeping it coherent can now be placed on processor hardware,” says Jim Mortensen, Software Architecture, Office of the CTO at Phoenix Technologies. One obvious indicator of the presence of virtualization features is in the CPU or system summary. For example, a “VT” in an Intel®-based system description stands for Intel Virtualization Technology, whether it’s as simple as “Dual-Core Intel® Core™ i5-650 3.20GHz 4MB Smart Cache (VT)” or this line from details for the Dell’s OptiPlex™ 980 desktop PC: “Intel® Core™ i7 Processor 870 /2.93GHz, 8M, VT-x, VT-d, TXT (vPro).” That can speed up your shopping. Intel’s CPU-level virtualization assists include Intel Virtualization Technology (Intel VT-x), Intel VT FlexMigration, Intel VT FlexPriority and Intel VT Extended Page Tables. Chipset tech includes Intel Virtualization Technology for Directed I/O (Intel VT-d), and at network-level, there’s Intel Virtualization Technology for Connectivity (Intel VT-c), along with VirtualMachine Device Queues (VMDq) and Virtual Machine Direct Connect (VMDc). Today, according to an Intel technology brief on their Xeon® 5500 processor (PDF), “Intel integrates hardware assists for virtualization into all key server components to help IT organizations consolidate more applications and heavier workloads on each server, and to improve flexibility, reliability and TCO.” (Except where noted, all Intel quotes in this article come from this same document.) “With support from the processor, chipset, BIOS, and enabling software, Intel VT improves traditional software-based virtualization,” says Intel. “Taking advantage of offloading workloads to system hardware, these integrated features enable virtualization software to provide more streamlined software stacks and “near native” performance characteristics.” For example, according to Intel’s Xeon tech brief, “Intel’s Xeon processor 5500 series has hardware-assist features for servers, including higher I/O bandwidth for higher virtualization performance plus multigeneration VM migration for flexibility in virtualized environments.” According to the same document, Intel Virtualization Technology (Intel VT) “enhances native virtualization performance by up to 2.1x and reduces roundtrip virtualization latency by up to 40 percent with hardware-enhanced technologies built into Intel processor, chipset and network adapter.” And here’s some more examples: “Intel VT FlexPriority creates a virtual copy of the APIC Task Priority Register (TPR), which can be read, and in some cases, changed by guest OSs without VMM intervention. This can deliver major performance improvements for 32-bit OSs that make frequent use of the TPR; for example, this can improve performance by as much as 35 percent for applications running on Windows® Server 2000.” Intel Virtualization Technology for Connectivity (Intel VT-c) provides hardware assist for network adapters, which are connecting servers to the network, to a storage infrastructure, and to other external devices. According to the Xeon brief, “Intel VT-c can more than double I/O throughput and achieve near-native throughput for virtualized applications, so more applications can be consolidated per server with fewer I/O bottlenecks.” Intel Virtualization Technology for Directed I/O (Intel VT-d). “For desktop virtualization, Intel VT-d speeds data movement and eliminates much of the performance overhead by reducing the need for VMM involvement in managing I/O traffic. Intel VT-d speeds data movement and eliminates much of the performance overhead by reducing the need for VMM involvement in managing I/O traffic.” According to Tom James, Manager of Desktop Virtualization Program, in the Business Client Platform Division, Intel, “Intel VT-D lets you assign a device like a graphics device to a particular VM, so it can get the full rich 3D experience, and graphics acceleration.” Intel Trusted Execution Technology (Intel TXT) secures the virtualization layer and virtualization software, via trusted execution, for client and server virtualization. For virtualization on the desktop in particular, “You want to make sure that the hypervisor hasn’t been tampered with. Intel TXT does this, measuring the hardware, before it executes,” says Phoenix’s Mortensen. Other virtualization-assisting features include Intel Flex Migration and AMD Extended Migration, used by tools like VMware Enhanced VMotion. According to Intel’s web site, “Intel VT FlexMigration is designed to enable seamless migrations among current and future Intel processor-based servers, even though newer systems may include enhanced instruction sets” — i.e., migrate running applications from one physical server to another that may have somewhat different hardware, without downtime.” Hardware features aren’t useful if the system isn’t aware of them. “We work very diligently to make sure that the BIOS provides the support that allows these features to work, and turns on these features,” says Phoenix’s Mortensen. For example, “Intel TXT works with the BIOS and with the motherboard’s Trusted Platform Module (TPM), so when you load the VM monitor — the hypervisor — you’re still in a trusted state. Looking Ahead In the works (or at least in research/development: hardware assists for: fault-tolerance in multithreaded (multiprocessor) systems VMs in combination with software: memory reliability, to let a platform survive an uncorrectable memory error, e.g. isolate an error to a single VM rather than impacting the whole platform, possibly better predict memory (DIMM) failures and stop using them before it fails “Intel EPT and AMD RVI are revolutionary and fundamental technologies to virtualization. Most future processor hardware assists will be more incremental in nature; each is valuable but by itself will have a small incremental effect,” notes Richard A. Brunner, chief platform architect for VMware. When you’re looking at doing virtualization, look for the hardware that will give your virtual machines real oomph. Related Information From Dell.com: Get Beyond the Status Quo.

Today’s CPUs, motherboards, even BIOS are improving virtualization performance.

Computer virtualization involves one or more virtual machines (VMs) emulating a hardware environment under a virtual machine monitor (VMM), a.k.a. hypervisor. It’s compute-intensive, to say the least. Modern computer virtualization began as software, but hardware is getting into the act – and, in the process, improving performance, including the number of VMs a host machine can run concurrently, and the effective cost per VM.

Faster, multicore processors make a difference, of course; and so does more RAM. But these aren’t enough.

Fortunately, today’s hardware includes a growing number and range of features specifically aimed at improving virtualization performance. Improved performance isn’t just execution speed; it also impacts the number of concurrent virtual machines a system can run. The security, reliability and flexibility of VMs are an issue too, such as the ability to move a VM from one hardware environment to another.

The earliest hardware assists for virtualization were Intel’s Extended Page Table (EPT) and AMD’s Rapid Virtualization Indexing (RVI) technologies, which let the hardware manage paging for a virtual machine, reducing virtualization’s overhead.

“With the introduction of EPT and RVI, most of the burden of managing the paging for a virtual machine and keeping it coherent can now be placed on processor hardware,” says Jim Mortensen, Software Architecture, Office of the CTO at Phoenix Technologies.

One obvious indicator of the presence of virtualization features is in the CPU or system summary. For example, a “VT” in an Intel®-based system description stands for Intel Virtualization Technology, whether it’s as simple as “Dual-Core Intel® Core™ i5-650 3.20GHz 4MB Smart Cache (VT)” or this line from details for the Dell’s OptiPlex™ 980 desktop PC: “Intel® Core™ i7 Processor 870 /2.93GHz, 8M, VT-x, VT-d, TXT (vPro).” That can speed up your shopping.

Intel’s CPU-level virtualization assists include Intel Virtualization Technology (Intel VT-x), Intel VT FlexMigration, Intel VT FlexPriority and Intel VT Extended Page Tables.

Chipset tech includes Intel Virtualization Technology for Directed I/O (Intel VT-d), and at network-level, there’s Intel Virtualization Technology for Connectivity (Intel VT-c), along with VirtualMachine Device Queues (VMDq) and Virtual Machine Direct Connect (VMDc).

Today, according to an Intel technology brief on their Xeon® 5500 processor (PDF), “Intel integrates hardware assists for virtualization into all key server components to help IT organizations consolidate more applications and heavier workloads on each server, and to improve flexibility, reliability and TCO.” (Except where noted, all Intel quotes in this article come from this same document.)

“With support from the processor, chipset, BIOS, and enabling software, Intel VT improves traditional software-based virtualization,” says Intel. “Taking advantage of offloading workloads to system hardware, these integrated features enable virtualization software to provide more streamlined software stacks and “near native” performance characteristics.”

For example, according to Intel’s Xeon tech brief, “Intel’s Xeon processor 5500 series has hardware-assist features for servers, including higher I/O bandwidth for higher virtualization performance plus multigeneration VM migration for flexibility in virtualized environments.”

According to the same document, Intel Virtualization Technology (Intel VT) “enhances native virtualization performance by up to 2.1x and reduces roundtrip virtualization latency by up to 40 percent with hardware-enhanced technologies built into Intel processor, chipset and network adapter.”

And here’s some more examples:

“Intel VT FlexPriority creates a virtual copy of the APIC Task Priority Register (TPR), which can be read, and in some cases, changed by guest OSs without VMM intervention. This can deliver major performance improvements for 32-bit OSs that make frequent use of the TPR; for example, this can improve performance by as much as 35 percent for applications running on Windows® Server 2000.”
Intel Virtualization Technology for Connectivity (Intel VT-c) provides hardware assist for network adapters, which are connecting servers to the network, to a storage infrastructure, and to other external devices. According to the Xeon brief, “Intel VT-c can more than double I/O throughput and achieve near-native throughput for virtualized applications, so more applications can be consolidated per server with fewer I/O bottlenecks.”
Intel Virtualization Technology for Directed I/O (Intel VT-d). “For desktop virtualization, Intel VT-d speeds data movement and eliminates much of the performance overhead by reducing the need for VMM involvement in managing I/O traffic. Intel VT-d speeds data movement and eliminates much of the performance overhead by reducing the need for VMM involvement in managing I/O traffic.”

According to Tom James, Manager of Desktop Virtualization Program, in the Business Client Platform Division, Intel, “Intel VT-D lets you assign a device like a graphics device to a particular VM, so it can get the full rich 3D experience, and graphics acceleration.”

Intel Trusted Execution Technology (Intel TXT) secures the virtualization layer and virtualization software, via trusted execution, for client and server virtualization. For virtualization on the desktop in particular, “You want to make sure that the hypervisor hasn’t been tampered with. Intel TXT does this, measuring the hardware, before it executes,” says Phoenix’s Mortensen.

Other virtualization-assisting features include Intel Flex Migration and AMD Extended Migration, used by tools like VMware Enhanced VMotion. According to Intel’s web site, “Intel VT FlexMigration is designed to enable seamless migrations among current and future Intel processor-based servers, even though newer systems may include enhanced instruction sets” — i.e., migrate running applications from one physical server to another that may have somewhat different hardware, without downtime.”

Hardware features aren’t useful if the system isn’t aware of them.

“We work very diligently to make sure that the BIOS provides the support that allows these features to work, and turns on these features,” says Phoenix’s Mortensen. For example, “Intel TXT works with the BIOS and with the motherboard’s Trusted Platform Module (TPM), so when you load the VM monitor — the hypervisor — you’re still in a trusted state.

Looking Ahead

In the works (or at least in research/development: hardware assists for:

fault-tolerance in multithreaded (multiprocessor) systems
VMs in combination with software: memory reliability, to let a platform survive an uncorrectable memory error, e.g. isolate an error to a single VM rather than impacting the whole platform, possibly better predict memory (DIMM) failures and stop using them before it fails

“Intel EPT and AMD RVI are revolutionary and fundamental technologies to virtualization. Most future processor hardware assists will be more incremental in nature; each is valuable but by itself will have a small incremental effect,” notes Richard A. Brunner, chief platform architect for VMware.

When you’re looking at doing virtualization, look for the hardware that will give your virtual machines real oomph.

Related Information From Dell.com: Get Beyond the Status Quo.