More OSes gain hypervisors, but most users choose OS-independent approach

Virtualization users can choose bare-metal hypervisors from VMware or run virtual machines through an operating system with Microsoft's Hyper-V or Red Hat's KVM.

With the rise of KVM and Hyper-V, the move is clearly afoot to build hypervisors into operating systems, but most users say the OS-independent approach to virtualization is here to stay.

Non-OS based virtualization from VMware can be expensive and resource-intensive because it requires tracking and licensing for virtual machines (VMs) running on disparate OSes. But it also provides much-needed features.

Advantages of the OS-based approach are exemplified by a Hackensack, N.J.-based virtualization user who hates the hassle of assigning VMware virtual machines (VMs) to OS licenses and struggles with tracking and managing VMs running outside the core OS. Some observers say these virtualization management burdens could cause a VMware defection to Red Hat KVM and Microsoft's Hyper-V, which can be built into and managed directly through an OS.

"Why spend money on [virtualization software], third-party tools, add-ons, and support contracts for a virtualization solution from a totally separate vendor when your OS -- Windows or Linux -- already has the same features built right into them," he wrote on a popular IT community board.

Non-OS hypervisor plusses and minuses
Microsoft's Hyper-V operates on bare metal and is typically used with Windows Server 2008, although Microsoft also supports SUSE Linux Enterprise Server 10 as guest OSes. KVM, or the Kernel-based Virtual Machine, is a Linux-based hypervisor for hosting Red Hat Enterprise Linux (RHEL), Windows, and Sun Microsystems' Solaris OS.

This user also complained about the licenses required by each OS running VMware VMs. "You have a separate financial transaction to worry about," with a separate company, where running Hyper-V VMs through Windows eliminates that concern. It should be noted that users who buy one Windows Server 2008 Enterprise Edition x64 with Hyper-V license get up to 4 Virtual Windows installations for free, but have to pay for anything beyond that.

Still, he went as far as to say the simplicity of OS-based hypervisors could make "the [non-OS] hypervisor totally irrelevant in the future. I think that VMware's days are numbered," he said.

And indeed, for many companies, VMware's high cost is a problem. One New Hampshire-based IT network engineer who uses the most basic version of VMware and Windows said his company won't pay for the loftier VMware Infrastructure (VI) packages like VI Standard - which costs $2,995 per two cores, plus annual support – because they want him to use Hyper-V in Windows.

But he doesn't think Hyper-V -- or any OS-based virtualization software for that matter -- can support all his data center needs and won't for a while. "VMware has about a 10-year head start," he said.

Eliminating OS bloatware
Still, the idea of running a heavy OS isn't appealing to all IT pros. "Consumers like me do not want their core based off a bloated OS," said a virtualization user and system administrator in the greater New York City area. "This is why the [non-OS] hypervisor will probably stay king for some time."

This camp says virtualization enables companies to run just an OS components they need, eliminating bloatware.

Gabrie van Zanten, a VMware administrator who blogs about virtualization, Gabe's Virtual World, concurred Lightweight OSes are "a big movement right now," and several companies are selling VMs packed with Just Enough Operating System (or JeOS) as virtual appliances.

The interest in packaging VMs with a bare-bones OS "shows that the hypervisor isn't going to the OS, because the OS is getting smaller and less important," van Zanten said.

The problem with running a full OS is the amount of resources it consumes and management it requires. Microsoft addressed this problem with its stripped-down Windows Server 2008 Server Core OS options.

The movement toward thin OSes is a reason why virtualization users like van Zanten say OS-based virtualization won't surpass the bare-metal hypervisor approach.

Thin is in (for hypervisors too)
While hypervisors continue to get thinner, such as VMware's ESXi , more hardware vendors are adding virtualization functions to their products, van Zanten said.

"What we can actually see right now is that the hypervisor itself gets smaller and smaller, and more functions are moved into the CPU," van Zanten said.

AMD and Intel both offer chips with virtualization-assist technologies to improve virtualization performance. The performance improvement provided by AMD Opteron's Rapid Virtualization Indexing (RVI) technology, for instance, increases with larger numbers of virtual CPUs (vCPU); with four vCPUs, RVI performed 42% better than CPUs using binary translation, according to VMware data.

The importance of VM management, support
Burton Group virtualization expert and analyst Chris Wolf said the IT pros he talks to care more about hypervisor virtualization management features than where a hypervisor is based or the cost.

"You have to weigh much more than the hypervisor and … look at lifecycle management, configuration management, lab management, orchestration and integration with enterprise management," he said.

Since VMware has the largest virtualization market share, it also has the largest vendor ecosystem and users can get all of those functions and more, Wolf said.

Microsoft's Hyper-V has a strong vendor support base as well, but the ecosystem around KVM is "pretty much nonexistent today ... [and] to assume that a Linux OS vendor is going to land in the top two anytime in the near future simply because virtualization is part of the OS is pretty farfetched," Wolf said.

"The vendor community is building management products to support VMware, Microsoft and Xen-based hypervisors. KVM support is years out on the roadmap because vendors aren't ready to invest in a platform where there is currently very little market," he said.

Meanwhile, Microsoft's OS-based approach to virtualization is gaining some traction, he said. "But again, the movement to a modularized data center, where the focus turns to containerized applications, means that the traditional OS doesn't have to do everything that it has done historically," Wolf said.

In fact, VMware has its own idea of what a virtualization-related OS should look like, and plans to introduce its Virtual Datacenter Operating System (VDC-OS) sometime this year. The "OS" will essentially be an extension of its existing VI platform with additional technologies used in virtualized environments like public and private clouds. "VMware sees itself as becoming what IT folks will think of when they talk about operating systems in five years," Wolf said.

Let us know what you think about the story; email Bridget Botelho, News Writer.

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